more attempts

vendor/github.com/juju/errors/LICENSE

@@ -0,0 +1,191 @@
+All files in this repository are licensed as follows. If you contribute
+to this repository, it is assumed that you license your contribution
+under the same license unless you state otherwise.
+
+All files Copyright (C) 2015 Canonical Ltd. unless otherwise specified in the file.
+
+This software is licensed under the LGPLv3, included below.
+
+As a special exception to the GNU Lesser General Public License version 3
+("LGPL3"), the copyright holders of this Library give you permission to
+convey to a third party a Combined Work that links statically or dynamically
+to this Library without providing any Minimal Corresponding Source or
+Minimal Application Code as set out in 4d or providing the installation
+information set out in section 4e, provided that you comply with the other
+provisions of LGPL3 and provided that you meet, for the Application the
+terms and conditions of the license(s) which apply to the Application.
+
+Except as stated in this special exception, the provisions of LGPL3 will
+continue to comply in full to this Library. If you modify this Library, you
+may apply this exception to your version of this Library, but you are not
+obliged to do so. If you do not wish to do so, delete this exception
+statement from your version. This exception does not (and cannot) modify any
+license terms which apply to the Application, with which you must still
+comply.
+
+
+                   GNU LESSER GENERAL PUBLIC LICENSE
+                       Version 3, 29 June 2007
+
+ Copyright (C) 2007 Free Software Foundation, Inc. <http://fsf.org/>
+ Everyone is permitted to copy and distribute verbatim copies
+ of this license document, but changing it is not allowed.
+
+
+  This version of the GNU Lesser General Public License incorporates
+the terms and conditions of version 3 of the GNU General Public
+License, supplemented by the additional permissions listed below.
+
+  0. Additional Definitions.
+
+  As used herein, "this License" refers to version 3 of the GNU Lesser
+General Public License, and the "GNU GPL" refers to version 3 of the GNU
+General Public License.
+
+  "The Library" refers to a covered work governed by this License,
+other than an Application or a Combined Work as defined below.
+
+  An "Application" is any work that makes use of an interface provided
+by the Library, but which is not otherwise based on the Library.
+Defining a subclass of a class defined by the Library is deemed a mode
+of using an interface provided by the Library.
+
+  A "Combined Work" is a work produced by combining or linking an
+Application with the Library.  The particular version of the Library
+with which the Combined Work was made is also called the "Linked
+Version".
+
+  The "Minimal Corresponding Source" for a Combined Work means the
+Corresponding Source for the Combined Work, excluding any source code
+for portions of the Combined Work that, considered in isolation, are
+based on the Application, and not on the Linked Version.
+
+  The "Corresponding Application Code" for a Combined Work means the
+object code and/or source code for the Application, including any data
+and utility programs needed for reproducing the Combined Work from the
+Application, but excluding the System Libraries of the Combined Work.
+
+  1. Exception to Section 3 of the GNU GPL.
+
+  You may convey a covered work under sections 3 and 4 of this License
+without being bound by section 3 of the GNU GPL.
+
+  2. Conveying Modified Versions.
+
+  If you modify a copy of the Library, and, in your modifications, a
+facility refers to a function or data to be supplied by an Application
+that uses the facility (other than as an argument passed when the
+facility is invoked), then you may convey a copy of the modified
+version:
+
+   a) under this License, provided that you make a good faith effort to
+   ensure that, in the event an Application does not supply the
+   function or data, the facility still operates, and performs
+   whatever part of its purpose remains meaningful, or
+
+   b) under the GNU GPL, with none of the additional permissions of
+   this License applicable to that copy.
+
+  3. Object Code Incorporating Material from Library Header Files.
+
+  The object code form of an Application may incorporate material from
+a header file that is part of the Library.  You may convey such object
+code under terms of your choice, provided that, if the incorporated
+material is not limited to numerical parameters, data structure
+layouts and accessors, or small macros, inline functions and templates
+(ten or fewer lines in length), you do both of the following:
+
+   a) Give prominent notice with each copy of the object code that the
+   Library is used in it and that the Library and its use are
+   covered by this License.
+
+   b) Accompany the object code with a copy of the GNU GPL and this license
+   document.
+
+  4. Combined Works.
+
+  You may convey a Combined Work under terms of your choice that,
+taken together, effectively do not restrict modification of the
+portions of the Library contained in the Combined Work and reverse
+engineering for debugging such modifications, if you also do each of
+the following:
+
+   a) Give prominent notice with each copy of the Combined Work that
+   the Library is used in it and that the Library and its use are
+   covered by this License.
+
+   b) Accompany the Combined Work with a copy of the GNU GPL and this license
+   document.
+
+   c) For a Combined Work that displays copyright notices during
+   execution, include the copyright notice for the Library among
+   these notices, as well as a reference directing the user to the
+   copies of the GNU GPL and this license document.
+
+   d) Do one of the following:
+
+       0) Convey the Minimal Corresponding Source under the terms of this
+       License, and the Corresponding Application Code in a form
+       suitable for, and under terms that permit, the user to
+       recombine or relink the Application with a modified version of
+       the Linked Version to produce a modified Combined Work, in the
+       manner specified by section 6 of the GNU GPL for conveying
+       Corresponding Source.
+
+       1) Use a suitable shared library mechanism for linking with the
+       Library.  A suitable mechanism is one that (a) uses at run time
+       a copy of the Library already present on the user's computer
+       system, and (b) will operate properly with a modified version
+       of the Library that is interface-compatible with the Linked
+       Version.
+
+   e) Provide Installation Information, but only if you would otherwise
+   be required to provide such information under section 6 of the
+   GNU GPL, and only to the extent that such information is
+   necessary to install and execute a modified version of the
+   Combined Work produced by recombining or relinking the
+   Application with a modified version of the Linked Version. (If
+   you use option 4d0, the Installation Information must accompany
+   the Minimal Corresponding Source and Corresponding Application
+   Code. If you use option 4d1, you must provide the Installation
+   Information in the manner specified by section 6 of the GNU GPL
+   for conveying Corresponding Source.)
+
+  5. Combined Libraries.
+
+  You may place library facilities that are a work based on the
+Library side by side in a single library together with other library
+facilities that are not Applications and are not covered by this
+License, and convey such a combined library under terms of your
+choice, if you do both of the following:
+
+   a) Accompany the combined library with a copy of the same work based
+   on the Library, uncombined with any other library facilities,
+   conveyed under the terms of this License.
+
+   b) Give prominent notice with the combined library that part of it
+   is a work based on the Library, and explaining where to find the
+   accompanying uncombined form of the same work.
+
+  6. Revised Versions of the GNU Lesser General Public License.
+
+  The Free Software Foundation may publish revised and/or new versions
+of the GNU Lesser General Public License from time to time. Such new
+versions will be similar in spirit to the present version, but may
+differ in detail to address new problems or concerns.
+
+  Each version is given a distinguishing version number. If the
+Library as you received it specifies that a certain numbered version
+of the GNU Lesser General Public License "or any later version"
+applies to it, you have the option of following the terms and
+conditions either of that published version or of any later version
+published by the Free Software Foundation. If the Library as you
+received it does not specify a version number of the GNU Lesser
+General Public License, you may choose any version of the GNU Lesser
+General Public License ever published by the Free Software Foundation.
+
+  If the Library as you received it specifies that a proxy can decide
+whether future versions of the GNU Lesser General Public License shall
+apply, that proxy's public statement of acceptance of any version is
+permanent authorization for you to choose that version for the
+Library.

vendor/github.com/juju/errors/Makefile

@@ -0,0 +1,11 @@
+default: check
+
+check:
+	go test && go test -compiler gccgo
+
+docs:
+	godoc2md github.com/juju/errors > README.md
+	sed -i 's|\[godoc-link-here\]|[![GoDoc](https://godoc.org/github.com/juju/errors?status.svg)](https://godoc.org/github.com/juju/errors)|' README.md 
+
+
+.PHONY: default check docs

vendor/github.com/juju/errors/README.md

@@ -0,0 +1,536 @@
+
+# errors
+    import "github.com/juju/errors"
+
+[![GoDoc](https://godoc.org/github.com/juju/errors?status.svg)](https://godoc.org/github.com/juju/errors)
+
+The juju/errors provides an easy way to annotate errors without losing the
+orginal error context.
+
+The exported `New` and `Errorf` functions are designed to replace the
+`errors.New` and `fmt.Errorf` functions respectively. The same underlying
+error is there, but the package also records the location at which the error
+was created.
+
+A primary use case for this library is to add extra context any time an
+error is returned from a function.
+
+
+	    if err := SomeFunc(); err != nil {
+		    return err
+		}
+
+This instead becomes:
+
+
+	    if err := SomeFunc(); err != nil {
+		    return errors.Trace(err)
+		}
+
+which just records the file and line number of the Trace call, or
+
+
+	    if err := SomeFunc(); err != nil {
+		    return errors.Annotate(err, "more context")
+		}
+
+which also adds an annotation to the error.
+
+When you want to check to see if an error is of a particular type, a helper
+function is normally exported by the package that returned the error, like the
+`os` package does.  The underlying cause of the error is available using the
+`Cause` function.
+
+
+	os.IsNotExist(errors.Cause(err))
+
+The result of the `Error()` call on an annotated error is the annotations joined
+with colons, then the result of the `Error()` method for the underlying error
+that was the cause.
+
+
+	err := errors.Errorf("original")
+	err = errors.Annotatef(err, "context")
+	err = errors.Annotatef(err, "more context")
+	err.Error() -> "more context: context: original"
+
+Obviously recording the file, line and functions is not very useful if you
+cannot get them back out again.
+
+
+	errors.ErrorStack(err)
+
+will return something like:
+
+
+	first error
+	github.com/juju/errors/annotation_test.go:193:
+	github.com/juju/errors/annotation_test.go:194: annotation
+	github.com/juju/errors/annotation_test.go:195:
+	github.com/juju/errors/annotation_test.go:196: more context
+	github.com/juju/errors/annotation_test.go:197:
+
+The first error was generated by an external system, so there was no location
+associated. The second, fourth, and last lines were generated with Trace calls,
+and the other two through Annotate.
+
+Sometimes when responding to an error you want to return a more specific error
+for the situation.
+
+
+	    if err := FindField(field); err != nil {
+		    return errors.Wrap(err, errors.NotFoundf(field))
+		}
+
+This returns an error where the complete error stack is still available, and
+`errors.Cause()` will return the `NotFound` error.
+
+
+
+
+
+
+## func AlreadyExistsf
+``` go
+func AlreadyExistsf(format string, args ...interface{}) error
+```
+AlreadyExistsf returns an error which satisfies IsAlreadyExists().
+
+
+## func Annotate
+``` go
+func Annotate(other error, message string) error
+```
+Annotate is used to add extra context to an existing error. The location of
+the Annotate call is recorded with the annotations. The file, line and
+function are also recorded.
+
+For example:
+
+
+	if err := SomeFunc(); err != nil {
+	    return errors.Annotate(err, "failed to frombulate")
+	}
+
+
+## func Annotatef
+``` go
+func Annotatef(other error, format string, args ...interface{}) error
+```
+Annotatef is used to add extra context to an existing error. The location of
+the Annotate call is recorded with the annotations. The file, line and
+function are also recorded.
+
+For example:
+
+
+	if err := SomeFunc(); err != nil {
+	    return errors.Annotatef(err, "failed to frombulate the %s", arg)
+	}
+
+
+## func Cause
+``` go
+func Cause(err error) error
+```
+Cause returns the cause of the given error.  This will be either the
+original error, or the result of a Wrap or Mask call.
+
+Cause is the usual way to diagnose errors that may have been wrapped by
+the other errors functions.
+
+
+## func DeferredAnnotatef
+``` go
+func DeferredAnnotatef(err *error, format string, args ...interface{})
+```
+DeferredAnnotatef annotates the given error (when it is not nil) with the given
+format string and arguments (like fmt.Sprintf). If *err is nil, DeferredAnnotatef
+does nothing. This method is used in a defer statement in order to annotate any
+resulting error with the same message.
+
+For example:
+
+
+	defer DeferredAnnotatef(&err, "failed to frombulate the %s", arg)
+
+
+## func Details
+``` go
+func Details(err error) string
+```
+Details returns information about the stack of errors wrapped by err, in
+the format:
+
+
+	[{filename:99: error one} {otherfile:55: cause of error one}]
+
+This is a terse alternative to ErrorStack as it returns a single line.
+
+
+## func ErrorStack
+``` go
+func ErrorStack(err error) string
+```
+ErrorStack returns a string representation of the annotated error. If the
+error passed as the parameter is not an annotated error, the result is
+simply the result of the Error() method on that error.
+
+If the error is an annotated error, a multi-line string is returned where
+each line represents one entry in the annotation stack. The full filename
+from the call stack is used in the output.
+
+
+	first error
+	github.com/juju/errors/annotation_test.go:193:
+	github.com/juju/errors/annotation_test.go:194: annotation
+	github.com/juju/errors/annotation_test.go:195:
+	github.com/juju/errors/annotation_test.go:196: more context
+	github.com/juju/errors/annotation_test.go:197:
+
+
+## func Errorf
+``` go
+func Errorf(format string, args ...interface{}) error
+```
+Errorf creates a new annotated error and records the location that the
+error is created.  This should be a drop in replacement for fmt.Errorf.
+
+For example:
+
+
+	return errors.Errorf("validation failed: %s", message)
+
+
+## func IsAlreadyExists
+``` go
+func IsAlreadyExists(err error) bool
+```
+IsAlreadyExists reports whether the error was created with
+AlreadyExistsf() or NewAlreadyExists().
+
+
+## func IsNotFound
+``` go
+func IsNotFound(err error) bool
+```
+IsNotFound reports whether err was created with NotFoundf() or
+NewNotFound().
+
+
+## func IsNotImplemented
+``` go
+func IsNotImplemented(err error) bool
+```
+IsNotImplemented reports whether err was created with
+NotImplementedf() or NewNotImplemented().
+
+
+## func IsNotSupported
+``` go
+func IsNotSupported(err error) bool
+```
+IsNotSupported reports whether the error was created with
+NotSupportedf() or NewNotSupported().
+
+
+## func IsNotValid
+``` go
+func IsNotValid(err error) bool
+```
+IsNotValid reports whether the error was created with NotValidf() or
+NewNotValid().
+
+
+## func IsUnauthorized
+``` go
+func IsUnauthorized(err error) bool
+```
+IsUnauthorized reports whether err was created with Unauthorizedf() or
+NewUnauthorized().
+
+
+## func Mask
+``` go
+func Mask(other error) error
+```
+Mask hides the underlying error type, and records the location of the masking.
+
+
+## func Maskf
+``` go
+func Maskf(other error, format string, args ...interface{}) error
+```
+Mask masks the given error with the given format string and arguments (like
+fmt.Sprintf), returning a new error that maintains the error stack, but
+hides the underlying error type.  The error string still contains the full
+annotations. If you want to hide the annotations, call Wrap.
+
+
+## func New
+``` go
+func New(message string) error
+```
+New is a drop in replacement for the standard libary errors module that records
+the location that the error is created.
+
+For example:
+
+
+	return errors.New("validation failed")
+
+
+## func NewAlreadyExists
+``` go
+func NewAlreadyExists(err error, msg string) error
+```
+NewAlreadyExists returns an error which wraps err and satisfies
+IsAlreadyExists().
+
+
+## func NewNotFound
+``` go
+func NewNotFound(err error, msg string) error
+```
+NewNotFound returns an error which wraps err that satisfies
+IsNotFound().
+
+
+## func NewNotImplemented
+``` go
+func NewNotImplemented(err error, msg string) error
+```
+NewNotImplemented returns an error which wraps err and satisfies
+IsNotImplemented().
+
+
+## func NewNotSupported
+``` go
+func NewNotSupported(err error, msg string) error
+```
+NewNotSupported returns an error which wraps err and satisfies
+IsNotSupported().
+
+
+## func NewNotValid
+``` go
+func NewNotValid(err error, msg string) error
+```
+NewNotValid returns an error which wraps err and satisfies IsNotValid().
+
+
+## func NewUnauthorized
+``` go
+func NewUnauthorized(err error, msg string) error
+```
+NewUnauthorized returns an error which wraps err and satisfies
+IsUnauthorized().
+
+
+## func NotFoundf
+``` go
+func NotFoundf(format string, args ...interface{}) error
+```
+NotFoundf returns an error which satisfies IsNotFound().
+
+
+## func NotImplementedf
+``` go
+func NotImplementedf(format string, args ...interface{}) error
+```
+NotImplementedf returns an error which satisfies IsNotImplemented().
+
+
+## func NotSupportedf
+``` go
+func NotSupportedf(format string, args ...interface{}) error
+```
+NotSupportedf returns an error which satisfies IsNotSupported().
+
+
+## func NotValidf
+``` go
+func NotValidf(format string, args ...interface{}) error
+```
+NotValidf returns an error which satisfies IsNotValid().
+
+
+## func Trace
+``` go
+func Trace(other error) error
+```
+Trace adds the location of the Trace call to the stack.  The Cause of the
+resulting error is the same as the error parameter.  If the other error is
+nil, the result will be nil.
+
+For example:
+
+
+	if err := SomeFunc(); err != nil {
+	    return errors.Trace(err)
+	}
+
+
+## func Unauthorizedf
+``` go
+func Unauthorizedf(format string, args ...interface{}) error
+```
+Unauthorizedf returns an error which satisfies IsUnauthorized().
+
+
+## func Wrap
+``` go
+func Wrap(other, newDescriptive error) error
+```
+Wrap changes the Cause of the error. The location of the Wrap call is also
+stored in the error stack.
+
+For example:
+
+
+	if err := SomeFunc(); err != nil {
+	    newErr := &packageError{"more context", private_value}
+	    return errors.Wrap(err, newErr)
+	}
+
+
+## func Wrapf
+``` go
+func Wrapf(other, newDescriptive error, format string, args ...interface{}) error
+```
+Wrapf changes the Cause of the error, and adds an annotation. The location
+of the Wrap call is also stored in the error stack.
+
+For example:
+
+
+	if err := SomeFunc(); err != nil {
+	    return errors.Wrapf(err, simpleErrorType, "invalid value %q", value)
+	}
+
+
+
+## type Err
+``` go
+type Err struct {
+    // contains filtered or unexported fields
+}
+```
+Err holds a description of an error along with information about
+where the error was created.
+
+It may be embedded in custom error types to add extra information that
+this errors package can understand.
+
+
+
+
+
+
+
+
+
+### func NewErr
+``` go
+func NewErr(format string, args ...interface{}) Err
+```
+NewErr is used to return an Err for the purpose of embedding in other
+structures.  The location is not specified, and needs to be set with a call
+to SetLocation.
+
+For example:
+
+
+	type FooError struct {
+	    errors.Err
+	    code int
+	}
+	
+	func NewFooError(code int) error {
+	    err := &FooError{errors.NewErr("foo"), code}
+	    err.SetLocation(1)
+	    return err
+	}
+
+
+
+
+### func (\*Err) Cause
+``` go
+func (e *Err) Cause() error
+```
+The Cause of an error is the most recent error in the error stack that
+meets one of these criteria: the original error that was raised; the new
+error that was passed into the Wrap function; the most recently masked
+error; or nil if the error itself is considered the Cause.  Normally this
+method is not invoked directly, but instead through the Cause stand alone
+function.
+
+
+
+### func (\*Err) Error
+``` go
+func (e *Err) Error() string
+```
+Error implements error.Error.
+
+
+
+### func (\*Err) Location
+``` go
+func (e *Err) Location() (filename string, line int)
+```
+Location is the file and line of where the error was most recently
+created or annotated.
+
+
+
+### func (\*Err) Message
+``` go
+func (e *Err) Message() string
+```
+Message returns the message stored with the most recent location. This is
+the empty string if the most recent call was Trace, or the message stored
+with Annotate or Mask.
+
+
+
+### func (\*Err) SetLocation
+``` go
+func (e *Err) SetLocation(callDepth int)
+```
+SetLocation records the source location of the error at callDepth stack
+frames above the call.
+
+
+
+### func (\*Err) StackTrace
+``` go
+func (e *Err) StackTrace() []string
+```
+StackTrace returns one string for each location recorded in the stack of
+errors. The first value is the originating error, with a line for each
+other annotation or tracing of the error.
+
+
+
+### func (\*Err) Underlying
+``` go
+func (e *Err) Underlying() error
+```
+Underlying returns the previous error in the error stack, if any. A client
+should not ever really call this method.  It is used to build the error
+stack and should not be introspected by client calls.  Or more
+specifically, clients should not depend on anything but the `Cause` of an
+error.
+
+
+
+
+
+
+
+
+
+- - -
+Generated by [godoc2md](http://godoc.org/github.com/davecheney/godoc2md)

vendor/github.com/juju/errors/doc.go

@@ -0,0 +1,81 @@
+// Copyright 2013, 2014 Canonical Ltd.
+// Licensed under the LGPLv3, see LICENCE file for details.
+
+/*
+[godoc-link-here]
+
+The juju/errors provides an easy way to annotate errors without losing the
+orginal error context.
+
+The exported `New` and `Errorf` functions are designed to replace the
+`errors.New` and `fmt.Errorf` functions respectively. The same underlying
+error is there, but the package also records the location at which the error
+was created.
+
+A primary use case for this library is to add extra context any time an
+error is returned from a function.
+
+    if err := SomeFunc(); err != nil {
+	    return err
+	}
+
+This instead becomes:
+
+    if err := SomeFunc(); err != nil {
+	    return errors.Trace(err)
+	}
+
+which just records the file and line number of the Trace call, or
+
+    if err := SomeFunc(); err != nil {
+	    return errors.Annotate(err, "more context")
+	}
+
+which also adds an annotation to the error.
+
+When you want to check to see if an error is of a particular type, a helper
+function is normally exported by the package that returned the error, like the
+`os` package does.  The underlying cause of the error is available using the
+`Cause` function.
+
+	os.IsNotExist(errors.Cause(err))
+
+The result of the `Error()` call on an annotated error is the annotations joined
+with colons, then the result of the `Error()` method for the underlying error
+that was the cause.
+
+	err := errors.Errorf("original")
+	err = errors.Annotatef(err, "context")
+	err = errors.Annotatef(err, "more context")
+	err.Error() -> "more context: context: original"
+
+Obviously recording the file, line and functions is not very useful if you
+cannot get them back out again.
+
+	errors.ErrorStack(err)
+
+will return something like:
+
+	first error
+	github.com/juju/errors/annotation_test.go:193:
+	github.com/juju/errors/annotation_test.go:194: annotation
+	github.com/juju/errors/annotation_test.go:195:
+	github.com/juju/errors/annotation_test.go:196: more context
+	github.com/juju/errors/annotation_test.go:197:
+
+The first error was generated by an external system, so there was no location
+associated. The second, fourth, and last lines were generated with Trace calls,
+and the other two through Annotate.
+
+Sometimes when responding to an error you want to return a more specific error
+for the situation.
+
+    if err := FindField(field); err != nil {
+	    return errors.Wrap(err, errors.NotFoundf(field))
+	}
+
+This returns an error where the complete error stack is still available, and
+`errors.Cause()` will return the `NotFound` error.
+
+*/
+package errors

vendor/github.com/juju/errors/error.go

@@ -0,0 +1,122 @@
+// Copyright 2014 Canonical Ltd.
+// Licensed under the LGPLv3, see LICENCE file for details.
+
+package errors
+
+import (
+	"fmt"
+	"reflect"
+	"runtime"
+)
+
+// Err holds a description of an error along with information about
+// where the error was created.
+//
+// It may be embedded in custom error types to add extra information that
+// this errors package can understand.
+type Err struct {
+	// message holds an annotation of the error.
+	message string
+
+	// cause holds the cause of the error as returned
+	// by the Cause method.
+	cause error
+
+	// previous holds the previous error in the error stack, if any.
+	previous error
+
+	// file and line hold the source code location where the error was
+	// created.
+	file string
+	line int
+}
+
+// NewErr is used to return an Err for the purpose of embedding in other
+// structures.  The location is not specified, and needs to be set with a call
+// to SetLocation.
+//
+// For example:
+//     type FooError struct {
+//         errors.Err
+//         code int
+//     }
+//
+//     func NewFooError(code int) error {
+//         err := &FooError{errors.NewErr("foo"), code}
+//         err.SetLocation(1)
+//         return err
+//     }
+func NewErr(format string, args ...interface{}) Err {
+	return Err{
+		message: fmt.Sprintf(format, args...),
+	}
+}
+
+// Location is the file and line of where the error was most recently
+// created or annotated.
+func (e *Err) Location() (filename string, line int) {
+	return e.file, e.line
+}
+
+// Underlying returns the previous error in the error stack, if any. A client
+// should not ever really call this method.  It is used to build the error
+// stack and should not be introspected by client calls.  Or more
+// specifically, clients should not depend on anything but the `Cause` of an
+// error.
+func (e *Err) Underlying() error {
+	return e.previous
+}
+
+// The Cause of an error is the most recent error in the error stack that
+// meets one of these criteria: the original error that was raised; the new
+// error that was passed into the Wrap function; the most recently masked
+// error; or nil if the error itself is considered the Cause.  Normally this
+// method is not invoked directly, but instead through the Cause stand alone
+// function.
+func (e *Err) Cause() error {
+	return e.cause
+}
+
+// Message returns the message stored with the most recent location. This is
+// the empty string if the most recent call was Trace, or the message stored
+// with Annotate or Mask.
+func (e *Err) Message() string {
+	return e.message
+}
+
+// Error implements error.Error.
+func (e *Err) Error() string {
+	// We want to walk up the stack of errors showing the annotations
+	// as long as the cause is the same.
+	err := e.previous
+	if !sameError(Cause(err), e.cause) && e.cause != nil {
+		err = e.cause
+	}
+	switch {
+	case err == nil:
+		return e.message
+	case e.message == "":
+		return err.Error()
+	}
+	return fmt.Sprintf("%s: %v", e.message, err)
+}
+
+// SetLocation records the source location of the error at callDepth stack
+// frames above the call.
+func (e *Err) SetLocation(callDepth int) {
+	_, file, line, _ := runtime.Caller(callDepth + 1)
+	e.file = trimGoPath(file)
+	e.line = line
+}
+
+// StackTrace returns one string for each location recorded in the stack of
+// errors. The first value is the originating error, with a line for each
+// other annotation or tracing of the error.
+func (e *Err) StackTrace() []string {
+	return errorStack(e)
+}
+
+// Ideally we'd have a way to check identity, but deep equals will do.
+func sameError(e1, e2 error) bool {
+	return reflect.DeepEqual(e1, e2)
+}

vendor/github.com/juju/errors/error_test.go

@@ -0,0 +1,161 @@
+// Copyright 2014 Canonical Ltd.
+// Licensed under the LGPLv3, see LICENCE file for details.
+
+package errors_test
+
+import (
+	"fmt"
+	"runtime"
+
+	jc "github.com/juju/testing/checkers"
+	gc "gopkg.in/check.v1"
+
+	"github.com/juju/errors"
+)
+
+type errorsSuite struct{}
+
+var _ = gc.Suite(&errorsSuite{})
+
+var someErr = errors.New("some error") //err varSomeErr
+
+func (*errorsSuite) TestErrorString(c *gc.C) {
+	for i, test := range []struct {
+		message   string
+		generator func() error
+		expected  string
+	}{
+		{
+			message: "uncomparable errors",
+			generator: func() error {
+				err := errors.Annotatef(newNonComparableError("uncomparable"), "annotation")
+				return errors.Annotatef(err, "another")
+			},
+			expected: "another: annotation: uncomparable",
+		}, {
+			message: "Errorf",
+			generator: func() error {
+				return errors.Errorf("first error")
+			},
+			expected: "first error",
+		}, {
+			message: "annotated error",
+			generator: func() error {
+				err := errors.Errorf("first error")
+				return errors.Annotatef(err, "annotation")
+			},
+			expected: "annotation: first error",
+		}, {
+			message: "test annotation format",
+			generator: func() error {
+				err := errors.Errorf("first %s", "error")
+				return errors.Annotatef(err, "%s", "annotation")
+			},
+			expected: "annotation: first error",
+		}, {
+			message: "wrapped error",
+			generator: func() error {
+				err := newError("first error")
+				return errors.Wrap(err, newError("detailed error"))
+			},
+			expected: "detailed error",
+		}, {
+			message: "wrapped annotated error",
+			generator: func() error {
+				err := errors.Errorf("first error")
+				err = errors.Annotatef(err, "annotated")
+				return errors.Wrap(err, fmt.Errorf("detailed error"))
+			},
+			expected: "detailed error",
+		}, {
+			message: "annotated wrapped error",
+			generator: func() error {
+				err := errors.Errorf("first error")
+				err = errors.Wrap(err, fmt.Errorf("detailed error"))
+				return errors.Annotatef(err, "annotated")
+			},
+			expected: "annotated: detailed error",
+		}, {
+			message: "traced, and annotated",
+			generator: func() error {
+				err := errors.New("first error")
+				err = errors.Trace(err)
+				err = errors.Annotate(err, "some context")
+				err = errors.Trace(err)
+				err = errors.Annotate(err, "more context")
+				return errors.Trace(err)
+			},
+			expected: "more context: some context: first error",
+		}, {
+			message: "traced, and annotated, masked and annotated",
+			generator: func() error {
+				err := errors.New("first error")
+				err = errors.Trace(err)
+				err = errors.Annotate(err, "some context")
+				err = errors.Maskf(err, "masked")
+				err = errors.Annotate(err, "more context")
+				return errors.Trace(err)
+			},
+			expected: "more context: masked: some context: first error",
+		},
+	} {
+		c.Logf("%v: %s", i, test.message)
+		err := test.generator()
+		ok := c.Check(err.Error(), gc.Equals, test.expected)
+		if !ok {
+			c.Logf("%#v", test.generator())
+		}
+	}
+}
+
+type embed struct {
+	errors.Err
+}
+
+func newEmbed(format string, args ...interface{}) *embed {
+	err := &embed{errors.NewErr(format, args...)}
+	err.SetLocation(1)
+	return err
+}
+
+func (*errorsSuite) TestNewErr(c *gc.C) {
+	if runtime.Compiler == "gccgo" {
+		c.Skip("gccgo can't determine the location")
+	}
+	err := newEmbed("testing %d", 42) //err embedErr
+	c.Assert(err.Error(), gc.Equals, "testing 42")
+	c.Assert(errors.Cause(err), gc.Equals, err)
+	c.Assert(errors.Details(err), jc.Contains, tagToLocation["embedErr"].String())
+}
+
+var _ error = (*embed)(nil)
+
+// This is an uncomparable error type, as it is a struct that supports the
+// error interface (as opposed to a pointer type).
+type error_ struct {
+	info  string
+	slice []string
+}
+
+// Create a non-comparable error
+func newNonComparableError(message string) error {
+	return error_{info: message}
+}
+
+func (e error_) Error() string {
+	return e.info
+}
+
+func newError(message string) error {
+	return testError{message}
+}
+
+// The testError is a value type error for ease of seeing results
+// when the test fails.
+type testError struct {
+	message string
+}
+
+func (e testError) Error() string {
+	return e.message
+}

vendor/github.com/juju/errors/errortypes.go

@@ -0,0 +1,284 @@
+// Copyright 2014 Canonical Ltd.
+// Licensed under the LGPLv3, see LICENCE file for details.
+
+package errors
+
+import (
+	"fmt"
+)
+
+// wrap is a helper to construct an *wrapper.
+func wrap(err error, format, suffix string, args ...interface{}) Err {
+	newErr := Err{
+		message:  fmt.Sprintf(format+suffix, args...),
+		previous: err,
+	}
+	newErr.SetLocation(2)
+	return newErr
+}
+
+// notFound represents an error when something has not been found.
+type notFound struct {
+	Err
+}
+
+// NotFoundf returns an error which satisfies IsNotFound().
+func NotFoundf(format string, args ...interface{}) error {
+	return &notFound{wrap(nil, format, " not found", args...)}
+}
+
+// NewNotFound returns an error which wraps err that satisfies
+// IsNotFound().
+func NewNotFound(err error, msg string) error {
+	return &notFound{wrap(err, msg, "")}
+}
+
+// IsNotFound reports whether err was created with NotFoundf() or
+// NewNotFound().
+func IsNotFound(err error) bool {
+	err = Cause(err)
+	_, ok := err.(*notFound)
+	return ok
+}
+
+// userNotFound represents an error when an inexistent user is looked up.
+type userNotFound struct {
+	Err
+}
+
+// UserNotFoundf returns an error which satisfies IsUserNotFound().
+func UserNotFoundf(format string, args ...interface{}) error {
+	return &userNotFound{wrap(nil, format, " user not found", args...)}
+}
+
+// NewUserNotFound returns an error which wraps err and satisfies
+// IsUserNotFound().
+func NewUserNotFound(err error, msg string) error {
+	return &userNotFound{wrap(err, msg, "")}
+}
+
+// IsUserNotFound reports whether err was created with UserNotFoundf() or
+// NewUserNotFound().
+func IsUserNotFound(err error) bool {
+	err = Cause(err)
+	_, ok := err.(*userNotFound)
+	return ok
+}
+
+// unauthorized represents an error when an operation is unauthorized.
+type unauthorized struct {
+	Err
+}
+
+// Unauthorizedf returns an error which satisfies IsUnauthorized().
+func Unauthorizedf(format string, args ...interface{}) error {
+	return &unauthorized{wrap(nil, format, "", args...)}
+}
+
+// NewUnauthorized returns an error which wraps err and satisfies
+// IsUnauthorized().
+func NewUnauthorized(err error, msg string) error {
+	return &unauthorized{wrap(err, msg, "")}
+}
+
+// IsUnauthorized reports whether err was created with Unauthorizedf() or
+// NewUnauthorized().
+func IsUnauthorized(err error) bool {
+	err = Cause(err)
+	_, ok := err.(*unauthorized)
+	return ok
+}
+
+// notImplemented represents an error when something is not
+// implemented.
+type notImplemented struct {
+	Err
+}
+
+// NotImplementedf returns an error which satisfies IsNotImplemented().
+func NotImplementedf(format string, args ...interface{}) error {
+	return &notImplemented{wrap(nil, format, " not implemented", args...)}
+}
+
+// NewNotImplemented returns an error which wraps err and satisfies
+// IsNotImplemented().
+func NewNotImplemented(err error, msg string) error {
+	return &notImplemented{wrap(err, msg, "")}
+}
+
+// IsNotImplemented reports whether err was created with
+// NotImplementedf() or NewNotImplemented().
+func IsNotImplemented(err error) bool {
+	err = Cause(err)
+	_, ok := err.(*notImplemented)
+	return ok
+}
+
+// alreadyExists represents and error when something already exists.
+type alreadyExists struct {
+	Err
+}
+
+// AlreadyExistsf returns an error which satisfies IsAlreadyExists().
+func AlreadyExistsf(format string, args ...interface{}) error {
+	return &alreadyExists{wrap(nil, format, " already exists", args...)}
+}
+
+// NewAlreadyExists returns an error which wraps err and satisfies
+// IsAlreadyExists().
+func NewAlreadyExists(err error, msg string) error {
+	return &alreadyExists{wrap(err, msg, "")}
+}
+
+// IsAlreadyExists reports whether the error was created with
+// AlreadyExistsf() or NewAlreadyExists().
+func IsAlreadyExists(err error) bool {
+	err = Cause(err)
+	_, ok := err.(*alreadyExists)
+	return ok
+}
+
+// notSupported represents an error when something is not supported.
+type notSupported struct {
+	Err
+}
+
+// NotSupportedf returns an error which satisfies IsNotSupported().
+func NotSupportedf(format string, args ...interface{}) error {
+	return &notSupported{wrap(nil, format, " not supported", args...)}
+}
+
+// NewNotSupported returns an error which wraps err and satisfies
+// IsNotSupported().
+func NewNotSupported(err error, msg string) error {
+	return &notSupported{wrap(err, msg, "")}
+}
+
+// IsNotSupported reports whether the error was created with
+// NotSupportedf() or NewNotSupported().
+func IsNotSupported(err error) bool {
+	err = Cause(err)
+	_, ok := err.(*notSupported)
+	return ok
+}
+
+// notValid represents an error when something is not valid.
+type notValid struct {
+	Err
+}
+
+// NotValidf returns an error which satisfies IsNotValid().
+func NotValidf(format string, args ...interface{}) error {
+	return &notValid{wrap(nil, format, " not valid", args...)}
+}
+
+// NewNotValid returns an error which wraps err and satisfies IsNotValid().
+func NewNotValid(err error, msg string) error {
+	return &notValid{wrap(err, msg, "")}
+}
+
+// IsNotValid reports whether the error was created with NotValidf() or
+// NewNotValid().
+func IsNotValid(err error) bool {
+	err = Cause(err)
+	_, ok := err.(*notValid)
+	return ok
+}
+
+// notProvisioned represents an error when something is not yet provisioned.
+type notProvisioned struct {
+	Err
+}
+
+// NotProvisionedf returns an error which satisfies IsNotProvisioned().
+func NotProvisionedf(format string, args ...interface{}) error {
+	return &notProvisioned{wrap(nil, format, " not provisioned", args...)}
+}
+
+// NewNotProvisioned returns an error which wraps err that satisfies
+// IsNotProvisioned().
+func NewNotProvisioned(err error, msg string) error {
+	return &notProvisioned{wrap(err, msg, "")}
+}
+
+// IsNotProvisioned reports whether err was created with NotProvisionedf() or
+// NewNotProvisioned().
+func IsNotProvisioned(err error) bool {
+	err = Cause(err)
+	_, ok := err.(*notProvisioned)
+	return ok
+}
+
+// notAssigned represents an error when something is not yet assigned to
+// something else.
+type notAssigned struct {
+	Err
+}
+
+// NotAssignedf returns an error which satisfies IsNotAssigned().
+func NotAssignedf(format string, args ...interface{}) error {
+	return &notAssigned{wrap(nil, format, " not assigned", args...)}
+}
+
+// NewNotAssigned returns an error which wraps err that satisfies
+// IsNotAssigned().
+func NewNotAssigned(err error, msg string) error {
+	return &notAssigned{wrap(err, msg, "")}
+}
+
+// IsNotAssigned reports whether err was created with NotAssignedf() or
+// NewNotAssigned().
+func IsNotAssigned(err error) bool {
+	err = Cause(err)
+	_, ok := err.(*notAssigned)
+	return ok
+}
+
+// badRequest represents an error when a request has bad parameters.
+type badRequest struct {
+	Err
+}
+
+// BadRequestf returns an error which satisfies IsBadRequest().
+func BadRequestf(format string, args ...interface{}) error {
+	return &badRequest{wrap(nil, format, "", args...)}
+}
+
+// NewBadRequest returns an error which wraps err that satisfies
+// IsBadRequest().
+func NewBadRequest(err error, msg string) error {
+	return &badRequest{wrap(err, msg, "")}
+}
+
+// IsBadRequest reports whether err was created with BadRequestf() or
+// NewBadRequest().
+func IsBadRequest(err error) bool {
+	err = Cause(err)
+	_, ok := err.(*badRequest)
+	return ok
+}
+
+// methodNotAllowed represents an error when an HTTP request
+// is made with an inappropriate method.
+type methodNotAllowed struct {
+	Err
+}
+
+// MethodNotAllowedf returns an error which satisfies IsMethodNotAllowed().
+func MethodNotAllowedf(format string, args ...interface{}) error {
+	return &methodNotAllowed{wrap(nil, format, "", args...)}
+}
+
+// NewMethodNotAllowed returns an error which wraps err that satisfies
+// IsMethodNotAllowed().
+func NewMethodNotAllowed(err error, msg string) error {
+	return &methodNotAllowed{wrap(err, msg, "")}
+}
+
+// IsMethodNotAllowed reports whether err was created with MethodNotAllowedf() or
+// NewMethodNotAllowed().
+func IsMethodNotAllowed(err error) bool {
+	err = Cause(err)
+	_, ok := err.(*methodNotAllowed)
+	return ok
+}

vendor/github.com/juju/errors/errortypes_test.go

@@ -0,0 +1,173 @@
+// Copyright 2013, 2014 Canonical Ltd.
+// Licensed under the LGPLv3, see LICENCE file for details.
+
+package errors_test
+
+import (
+	stderrors "errors"
+	"fmt"
+	"reflect"
+	"runtime"
+
+	"github.com/juju/errors"
+	jc "github.com/juju/testing/checkers"
+	gc "gopkg.in/check.v1"
+)
+
+// errorInfo holds information about a single error type: a satisfier
+// function, wrapping and variable arguments constructors and message
+// suffix.
+type errorInfo struct {
+	satisfier       func(error) bool
+	argsConstructor func(string, ...interface{}) error
+	wrapConstructor func(error, string) error
+	suffix          string
+}
+
+// allErrors holds information for all defined errors. When adding new
+// errors, add them here as well to include them in tests.
+var allErrors = []*errorInfo{
+	&errorInfo{errors.IsNotFound, errors.NotFoundf, errors.NewNotFound, " not found"},
+	&errorInfo{errors.IsUserNotFound, errors.UserNotFoundf, errors.NewUserNotFound, " user not found"},
+	&errorInfo{errors.IsUnauthorized, errors.Unauthorizedf, errors.NewUnauthorized, ""},
+	&errorInfo{errors.IsNotImplemented, errors.NotImplementedf, errors.NewNotImplemented, " not implemented"},
+	&errorInfo{errors.IsAlreadyExists, errors.AlreadyExistsf, errors.NewAlreadyExists, " already exists"},
+	&errorInfo{errors.IsNotSupported, errors.NotSupportedf, errors.NewNotSupported, " not supported"},
+	&errorInfo{errors.IsNotValid, errors.NotValidf, errors.NewNotValid, " not valid"},
+	&errorInfo{errors.IsNotProvisioned, errors.NotProvisionedf, errors.NewNotProvisioned, " not provisioned"},
+	&errorInfo{errors.IsNotAssigned, errors.NotAssignedf, errors.NewNotAssigned, " not assigned"},
+	&errorInfo{errors.IsMethodNotAllowed, errors.MethodNotAllowedf, errors.NewMethodNotAllowed, ""},
+	&errorInfo{errors.IsBadRequest, errors.BadRequestf, errors.NewBadRequest, ""},
+}
+
+type errorTypeSuite struct{}
+
+var _ = gc.Suite(&errorTypeSuite{})
+
+func (t *errorInfo) satisfierName() string {
+	value := reflect.ValueOf(t.satisfier)
+	f := runtime.FuncForPC(value.Pointer())
+	return f.Name()
+}
+
+func (t *errorInfo) equal(t0 *errorInfo) bool {
+	if t0 == nil {
+		return false
+	}
+	return t.satisfierName() == t0.satisfierName()
+}
+
+type errorTest struct {
+	err     error
+	message string
+	errInfo *errorInfo
+}
+
+func deferredAnnotatef(err error, format string, args ...interface{}) error {
+	errors.DeferredAnnotatef(&err, format, args...)
+	return err
+}
+
+func mustSatisfy(c *gc.C, err error, errInfo *errorInfo) {
+	if errInfo != nil {
+		msg := fmt.Sprintf("%#v must satisfy %v", err, errInfo.satisfierName())
+		c.Check(err, jc.Satisfies, errInfo.satisfier, gc.Commentf(msg))
+	}
+}
+
+func mustNotSatisfy(c *gc.C, err error, errInfo *errorInfo) {
+	if errInfo != nil {
+		msg := fmt.Sprintf("%#v must not satisfy %v", err, errInfo.satisfierName())
+		c.Check(err, gc.Not(jc.Satisfies), errInfo.satisfier, gc.Commentf(msg))
+	}
+}
+
+func checkErrorMatches(c *gc.C, err error, message string, errInfo *errorInfo) {
+	if message == "<nil>" {
+		c.Check(err, gc.IsNil)
+		c.Check(errInfo, gc.IsNil)
+	} else {
+		c.Check(err, gc.ErrorMatches, message)
+	}
+}
+
+func runErrorTests(c *gc.C, errorTests []errorTest, checkMustSatisfy bool) {
+	for i, t := range errorTests {
+		c.Logf("test %d: %T: %v", i, t.err, t.err)
+		checkErrorMatches(c, t.err, t.message, t.errInfo)
+		if checkMustSatisfy {
+			mustSatisfy(c, t.err, t.errInfo)
+		}
+
+		// Check all other satisfiers to make sure none match.
+		for _, otherErrInfo := range allErrors {
+			if checkMustSatisfy && otherErrInfo.equal(t.errInfo) {
+				continue
+			}
+			mustNotSatisfy(c, t.err, otherErrInfo)
+		}
+	}
+}
+
+func (*errorTypeSuite) TestDeferredAnnotatef(c *gc.C) {
+	// Ensure DeferredAnnotatef annotates the errors.
+	errorTests := []errorTest{}
+	for _, errInfo := range allErrors {
+		errorTests = append(errorTests, []errorTest{{
+			deferredAnnotatef(nil, "comment"),
+			"<nil>",
+			nil,
+		}, {
+			deferredAnnotatef(stderrors.New("blast"), "comment"),
+			"comment: blast",
+			nil,
+		}, {
+			deferredAnnotatef(errInfo.argsConstructor("foo %d", 42), "comment %d", 69),
+			"comment 69: foo 42" + errInfo.suffix,
+			errInfo,
+		}, {
+			deferredAnnotatef(errInfo.argsConstructor(""), "comment"),
+			"comment: " + errInfo.suffix,
+			errInfo,
+		}, {
+			deferredAnnotatef(errInfo.wrapConstructor(stderrors.New("pow!"), "woo"), "comment"),
+			"comment: woo: pow!",
+			errInfo,
+		}}...)
+	}
+
+	runErrorTests(c, errorTests, true)
+}
+
+func (*errorTypeSuite) TestAllErrors(c *gc.C) {
+	errorTests := []errorTest{}
+	for _, errInfo := range allErrors {
+		errorTests = append(errorTests, []errorTest{{
+			nil,
+			"<nil>",
+			nil,
+		}, {
+			errInfo.argsConstructor("foo %d", 42),
+			"foo 42" + errInfo.suffix,
+			errInfo,
+		}, {
+			errInfo.argsConstructor(""),
+			errInfo.suffix,
+			errInfo,
+		}, {
+			errInfo.wrapConstructor(stderrors.New("pow!"), "prefix"),
+			"prefix: pow!",
+			errInfo,
+		}, {
+			errInfo.wrapConstructor(stderrors.New("pow!"), ""),
+			"pow!",
+			errInfo,
+		}, {
+			errInfo.wrapConstructor(nil, "prefix"),
+			"prefix",
+			errInfo,
+		}}...)
+	}
+
+	runErrorTests(c, errorTests, true)
+}

vendor/github.com/juju/errors/example_test.go

@@ -0,0 +1,23 @@
+// Copyright 2013, 2014 Canonical Ltd.
+// Licensed under the LGPLv3, see LICENCE file for details.
+
+package errors_test
+
+import (
+	"fmt"
+
+	"github.com/juju/errors"
+)
+
+func ExampleTrace() {
+	var err1 error = fmt.Errorf("something wicked this way comes")
+	var err2 error = nil
+
+	// Tracing a non nil error will return an error
+	fmt.Println(errors.Trace(err1))
+	// Tracing nil will return nil
+	fmt.Println(errors.Trace(err2))
+
+	// Output: something wicked this way comes
+	// <nil>
+}

vendor/github.com/juju/errors/export_test.go

@@ -0,0 +1,12 @@
+// Copyright 2013, 2014 Canonical Ltd.
+// Licensed under the LGPLv3, see LICENCE file for details.
+
+package errors
+
+// Since variables are declared before the init block, in order to get the goPath
+// we need to return it rather than just reference it.
+func GoPath() string {
+	return goPath
+}
+
+var TrimGoPath = trimGoPath

vendor/github.com/juju/errors/functions.go

@@ -0,0 +1,330 @@
+// Copyright 2014 Canonical Ltd.
+// Licensed under the LGPLv3, see LICENCE file for details.
+
+package errors
+
+import (
+	"fmt"
+	"strings"
+)
+
+// New is a drop in replacement for the standard libary errors module that records
+// the location that the error is created.
+//
+// For example:
+//    return errors.New("validation failed")
+//
+func New(message string) error {
+	err := &Err{message: message}
+	err.SetLocation(1)
+	return err
+}
+
+// Errorf creates a new annotated error and records the location that the
+// error is created.  This should be a drop in replacement for fmt.Errorf.
+//
+// For example:
+//    return errors.Errorf("validation failed: %s", message)
+//
+func Errorf(format string, args ...interface{}) error {
+	err := &Err{message: fmt.Sprintf(format, args...)}
+	err.SetLocation(1)
+	return err
+}
+
+// Trace adds the location of the Trace call to the stack.  The Cause of the
+// resulting error is the same as the error parameter.  If the other error is
+// nil, the result will be nil.
+//
+// For example:
+//   if err := SomeFunc(); err != nil {
+//       return errors.Trace(err)
+//   }
+//
+func Trace(other error) error {
+	if other == nil {
+		return nil
+	}
+	err := &Err{previous: other, cause: Cause(other)}
+	err.SetLocation(1)
+	return err
+}
+
+// Annotate is used to add extra context to an existing error. The location of
+// the Annotate call is recorded with the annotations. The file, line and
+// function are also recorded.
+//
+// For example:
+//   if err := SomeFunc(); err != nil {
+//       return errors.Annotate(err, "failed to frombulate")
+//   }
+//
+func Annotate(other error, message string) error {
+	if other == nil {
+		return nil
+	}
+	err := &Err{
+		previous: other,
+		cause:    Cause(other),
+		message:  message,
+	}
+	err.SetLocation(1)
+	return err
+}
+
+// Annotatef is used to add extra context to an existing error. The location of
+// the Annotate call is recorded with the annotations. The file, line and
+// function are also recorded.
+//
+// For example:
+//   if err := SomeFunc(); err != nil {
+//       return errors.Annotatef(err, "failed to frombulate the %s", arg)
+//   }
+//
+func Annotatef(other error, format string, args ...interface{}) error {
+	if other == nil {
+		return nil
+	}
+	err := &Err{
+		previous: other,
+		cause:    Cause(other),
+		message:  fmt.Sprintf(format, args...),
+	}
+	err.SetLocation(1)
+	return err
+}
+
+// DeferredAnnotatef annotates the given error (when it is not nil) with the given
+// format string and arguments (like fmt.Sprintf). If *err is nil, DeferredAnnotatef
+// does nothing. This method is used in a defer statement in order to annotate any
+// resulting error with the same message.
+//
+// For example:
+//
+//    defer DeferredAnnotatef(&err, "failed to frombulate the %s", arg)
+//
+func DeferredAnnotatef(err *error, format string, args ...interface{}) {
+	if *err == nil {
+		return
+	}
+	newErr := &Err{
+		message:  fmt.Sprintf(format, args...),
+		cause:    Cause(*err),
+		previous: *err,
+	}
+	newErr.SetLocation(1)
+	*err = newErr
+}
+
+// Wrap changes the Cause of the error. The location of the Wrap call is also
+// stored in the error stack.
+//
+// For example:
+//   if err := SomeFunc(); err != nil {
+//       newErr := &packageError{"more context", private_value}
+//       return errors.Wrap(err, newErr)
+//   }
+//
+func Wrap(other, newDescriptive error) error {
+	err := &Err{
+		previous: other,
+		cause:    newDescriptive,
+	}
+	err.SetLocation(1)
+	return err
+}
+
+// Wrapf changes the Cause of the error, and adds an annotation. The location
+// of the Wrap call is also stored in the error stack.
+//
+// For example:
+//   if err := SomeFunc(); err != nil {
+//       return errors.Wrapf(err, simpleErrorType, "invalid value %q", value)
+//   }
+//
+func Wrapf(other, newDescriptive error, format string, args ...interface{}) error {
+	err := &Err{
+		message:  fmt.Sprintf(format, args...),
+		previous: other,
+		cause:    newDescriptive,
+	}
+	err.SetLocation(1)
+	return err
+}
+
+// Mask masks the given error with the given format string and arguments (like
+// fmt.Sprintf), returning a new error that maintains the error stack, but
+// hides the underlying error type.  The error string still contains the full
+// annotations. If you want to hide the annotations, call Wrap.
+func Maskf(other error, format string, args ...interface{}) error {
+	if other == nil {
+		return nil
+	}
+	err := &Err{
+		message:  fmt.Sprintf(format, args...),
+		previous: other,
+	}
+	err.SetLocation(1)
+	return err
+}
+
+// Mask hides the underlying error type, and records the location of the masking.
+func Mask(other error) error {
+	if other == nil {
+		return nil
+	}
+	err := &Err{
+		previous: other,
+	}
+	err.SetLocation(1)
+	return err
+}
+
+// Cause returns the cause of the given error.  This will be either the
+// original error, or the result of a Wrap or Mask call.
+//
+// Cause is the usual way to diagnose errors that may have been wrapped by
+// the other errors functions.
+func Cause(err error) error {
+	var diag error
+	if err, ok := err.(causer); ok {
+		diag = err.Cause()
+	}
+	if diag != nil {
+		return diag
+	}
+	return err
+}
+
+type causer interface {
+	Cause() error
+}
+
+type wrapper interface {
+	// Message returns the top level error message,
+	// not including the message from the Previous
+	// error.
+	Message() string
+
+	// Underlying returns the Previous error, or nil
+	// if there is none.
+	Underlying() error
+}
+
+type locationer interface {
+	Location() (string, int)
+}
+
+var (
+	_ wrapper    = (*Err)(nil)
+	_ locationer = (*Err)(nil)
+	_ causer     = (*Err)(nil)
+)
+
+// Details returns information about the stack of errors wrapped by err, in
+// the format:
+//
+// 	[{filename:99: error one} {otherfile:55: cause of error one}]
+//
+// This is a terse alternative to ErrorStack as it returns a single line.
+func Details(err error) string {
+	if err == nil {
+		return "[]"
+	}
+	var s []byte
+	s = append(s, '[')
+	for {
+		s = append(s, '{')
+		if err, ok := err.(locationer); ok {
+			file, line := err.Location()
+			if file != "" {
+				s = append(s, fmt.Sprintf("%s:%d", file, line)...)
+				s = append(s, ": "...)
+			}
+		}
+		if cerr, ok := err.(wrapper); ok {
+			s = append(s, cerr.Message()...)
+			err = cerr.Underlying()
+		} else {
+			s = append(s, err.Error()...)
+			err = nil
+		}
+		s = append(s, '}')
+		if err == nil {
+			break
+		}
+		s = append(s, ' ')
+	}
+	s = append(s, ']')
+	return string(s)
+}
+
+// ErrorStack returns a string representation of the annotated error. If the
+// error passed as the parameter is not an annotated error, the result is
+// simply the result of the Error() method on that error.
+//
+// If the error is an annotated error, a multi-line string is returned where
+// each line represents one entry in the annotation stack. The full filename
+// from the call stack is used in the output.
+//
+//     first error
+//     github.com/juju/errors/annotation_test.go:193:
+//     github.com/juju/errors/annotation_test.go:194: annotation
+//     github.com/juju/errors/annotation_test.go:195:
+//     github.com/juju/errors/annotation_test.go:196: more context
+//     github.com/juju/errors/annotation_test.go:197:
+func ErrorStack(err error) string {
+	return strings.Join(errorStack(err), "\n")
+}
+
+func errorStack(err error) []string {
+	if err == nil {
+		return nil
+	}
+
+	// We want the first error first
+	var lines []string
+	for {
+		var buff []byte
+		if err, ok := err.(locationer); ok {
+			file, line := err.Location()
+			// Strip off the leading GOPATH/src path elements.
+			file = trimGoPath(file)
+			if file != "" {
+				buff = append(buff, fmt.Sprintf("%s:%d", file, line)...)
+				buff = append(buff, ": "...)
+			}
+		}
+		if cerr, ok := err.(wrapper); ok {
+			message := cerr.Message()
+			buff = append(buff, message...)
+			// If there is a cause for this error, and it is different to the cause
+			// of the underlying error, then output the error string in the stack trace.
+			var cause error
+			if err1, ok := err.(causer); ok {
+				cause = err1.Cause()
+			}
+			err = cerr.Underlying()
+			if cause != nil && !sameError(Cause(err), cause) {
+				if message != "" {
+					buff = append(buff, ": "...)
+				}
+				buff = append(buff, cause.Error()...)
+			}
+		} else {
+			buff = append(buff, err.Error()...)
+			err = nil
+		}
+		lines = append(lines, string(buff))
+		if err == nil {
+			break
+		}
+	}
+	// reverse the lines to get the original error, which was at the end of
+	// the list, back to the start.
+	var result []string
+	for i := len(lines); i > 0; i-- {
+		result = append(result, lines[i-1])
+	}
+	return result
+}

vendor/github.com/juju/errors/functions_test.go

@@ -0,0 +1,305 @@
+// Copyright 2014 Canonical Ltd.
+// Licensed under the LGPLv3, see LICENCE file for details.
+
+package errors_test
+
+import (
+	"fmt"
+	"os"
+	"path/filepath"
+	"runtime"
+	"strings"
+
+	jc "github.com/juju/testing/checkers"
+	gc "gopkg.in/check.v1"
+
+	"github.com/juju/errors"
+)
+
+type functionSuite struct {
+}
+
+var _ = gc.Suite(&functionSuite{})
+
+func (*functionSuite) TestNew(c *gc.C) {
+	err := errors.New("testing") //err newTest
+	c.Assert(err.Error(), gc.Equals, "testing")
+	c.Assert(errors.Cause(err), gc.Equals, err)
+	c.Assert(errors.Details(err), jc.Contains, tagToLocation["newTest"].String())
+}
+
+func (*functionSuite) TestErrorf(c *gc.C) {
+	err := errors.Errorf("testing %d", 42) //err errorfTest
+	c.Assert(err.Error(), gc.Equals, "testing 42")
+	c.Assert(errors.Cause(err), gc.Equals, err)
+	c.Assert(errors.Details(err), jc.Contains, tagToLocation["errorfTest"].String())
+}
+
+func (*functionSuite) TestTrace(c *gc.C) {
+	first := errors.New("first")
+	err := errors.Trace(first) //err traceTest
+	c.Assert(err.Error(), gc.Equals, "first")
+	c.Assert(errors.Cause(err), gc.Equals, first)
+	c.Assert(errors.Details(err), jc.Contains, tagToLocation["traceTest"].String())
+
+	c.Assert(errors.Trace(nil), gc.IsNil)
+}
+
+func (*functionSuite) TestAnnotate(c *gc.C) {
+	first := errors.New("first")
+	err := errors.Annotate(first, "annotation") //err annotateTest
+	c.Assert(err.Error(), gc.Equals, "annotation: first")
+	c.Assert(errors.Cause(err), gc.Equals, first)
+	c.Assert(errors.Details(err), jc.Contains, tagToLocation["annotateTest"].String())
+
+	c.Assert(errors.Annotate(nil, "annotate"), gc.IsNil)
+}
+
+func (*functionSuite) TestAnnotatef(c *gc.C) {
+	first := errors.New("first")
+	err := errors.Annotatef(first, "annotation %d", 2) //err annotatefTest
+	c.Assert(err.Error(), gc.Equals, "annotation 2: first")
+	c.Assert(errors.Cause(err), gc.Equals, first)
+	c.Assert(errors.Details(err), jc.Contains, tagToLocation["annotatefTest"].String())
+
+	c.Assert(errors.Annotatef(nil, "annotate"), gc.IsNil)
+}
+
+func (*functionSuite) TestDeferredAnnotatef(c *gc.C) {
+	// NOTE: this test fails with gccgo
+	if runtime.Compiler == "gccgo" {
+		c.Skip("gccgo can't determine the location")
+	}
+	first := errors.New("first")
+	test := func() (err error) {
+		defer errors.DeferredAnnotatef(&err, "deferred %s", "annotate")
+		return first
+	} //err deferredAnnotate
+	err := test()
+	c.Assert(err.Error(), gc.Equals, "deferred annotate: first")
+	c.Assert(errors.Cause(err), gc.Equals, first)
+	c.Assert(errors.Details(err), jc.Contains, tagToLocation["deferredAnnotate"].String())
+
+	err = nil
+	errors.DeferredAnnotatef(&err, "deferred %s", "annotate")
+	c.Assert(err, gc.IsNil)
+}
+
+func (*functionSuite) TestWrap(c *gc.C) {
+	first := errors.New("first") //err wrapFirst
+	detailed := errors.New("detailed")
+	err := errors.Wrap(first, detailed) //err wrapTest
+	c.Assert(err.Error(), gc.Equals, "detailed")
+	c.Assert(errors.Cause(err), gc.Equals, detailed)
+	c.Assert(errors.Details(err), jc.Contains, tagToLocation["wrapFirst"].String())
+	c.Assert(errors.Details(err), jc.Contains, tagToLocation["wrapTest"].String())
+}
+
+func (*functionSuite) TestWrapOfNil(c *gc.C) {
+	detailed := errors.New("detailed")
+	err := errors.Wrap(nil, detailed) //err nilWrapTest
+	c.Assert(err.Error(), gc.Equals, "detailed")
+	c.Assert(errors.Cause(err), gc.Equals, detailed)
+	c.Assert(errors.Details(err), jc.Contains, tagToLocation["nilWrapTest"].String())
+}
+
+func (*functionSuite) TestWrapf(c *gc.C) {
+	first := errors.New("first") //err wrapfFirst
+	detailed := errors.New("detailed")
+	err := errors.Wrapf(first, detailed, "value %d", 42) //err wrapfTest
+	c.Assert(err.Error(), gc.Equals, "value 42: detailed")
+	c.Assert(errors.Cause(err), gc.Equals, detailed)
+	c.Assert(errors.Details(err), jc.Contains, tagToLocation["wrapfFirst"].String())
+	c.Assert(errors.Details(err), jc.Contains, tagToLocation["wrapfTest"].String())
+}
+
+func (*functionSuite) TestWrapfOfNil(c *gc.C) {
+	detailed := errors.New("detailed")
+	err := errors.Wrapf(nil, detailed, "value %d", 42) //err nilWrapfTest
+	c.Assert(err.Error(), gc.Equals, "value 42: detailed")
+	c.Assert(errors.Cause(err), gc.Equals, detailed)
+	c.Assert(errors.Details(err), jc.Contains, tagToLocation["nilWrapfTest"].String())
+}
+
+func (*functionSuite) TestMask(c *gc.C) {
+	first := errors.New("first")
+	err := errors.Mask(first) //err maskTest
+	c.Assert(err.Error(), gc.Equals, "first")
+	c.Assert(errors.Cause(err), gc.Equals, err)
+	c.Assert(errors.Details(err), jc.Contains, tagToLocation["maskTest"].String())
+
+	c.Assert(errors.Mask(nil), gc.IsNil)
+}
+
+func (*functionSuite) TestMaskf(c *gc.C) {
+	first := errors.New("first")
+	err := errors.Maskf(first, "masked %d", 42) //err maskfTest
+	c.Assert(err.Error(), gc.Equals, "masked 42: first")
+	c.Assert(errors.Cause(err), gc.Equals, err)
+	c.Assert(errors.Details(err), jc.Contains, tagToLocation["maskfTest"].String())
+
+	c.Assert(errors.Maskf(nil, "mask"), gc.IsNil)
+}
+
+func (*functionSuite) TestCause(c *gc.C) {
+	c.Assert(errors.Cause(nil), gc.IsNil)
+	c.Assert(errors.Cause(someErr), gc.Equals, someErr)
+
+	fmtErr := fmt.Errorf("simple")
+	c.Assert(errors.Cause(fmtErr), gc.Equals, fmtErr)
+
+	err := errors.Wrap(someErr, fmtErr)
+	c.Assert(errors.Cause(err), gc.Equals, fmtErr)
+
+	err = errors.Annotate(err, "annotated")
+	c.Assert(errors.Cause(err), gc.Equals, fmtErr)
+
+	err = errors.Maskf(err, "maksed")
+	c.Assert(errors.Cause(err), gc.Equals, err)
+
+	// Look for a file that we know isn't there.
+	dir := c.MkDir()
+	_, err = os.Stat(filepath.Join(dir, "not-there"))
+	c.Assert(os.IsNotExist(err), jc.IsTrue)
+
+	err = errors.Annotatef(err, "wrap it")
+	// Now the error itself isn't a 'IsNotExist'.
+	c.Assert(os.IsNotExist(err), jc.IsFalse)
+	// However if we use the Check method, it is.
+	c.Assert(os.IsNotExist(errors.Cause(err)), jc.IsTrue)
+}
+
+func (s *functionSuite) TestDetails(c *gc.C) {
+	if runtime.Compiler == "gccgo" {
+		c.Skip("gccgo can't determine the location")
+	}
+	c.Assert(errors.Details(nil), gc.Equals, "[]")
+
+	otherErr := fmt.Errorf("other")
+	checkDetails(c, otherErr, "[{other}]")
+
+	err0 := newEmbed("foo") //err TestStack#0
+	checkDetails(c, err0, "[{$TestStack#0$: foo}]")
+
+	err1 := errors.Annotate(err0, "bar") //err TestStack#1
+	checkDetails(c, err1, "[{$TestStack#1$: bar} {$TestStack#0$: foo}]")
+
+	err2 := errors.Trace(err1) //err TestStack#2
+	checkDetails(c, err2, "[{$TestStack#2$: } {$TestStack#1$: bar} {$TestStack#0$: foo}]")
+}
+
+type tracer interface {
+	StackTrace() []string
+}
+
+func (*functionSuite) TestErrorStack(c *gc.C) {
+	for i, test := range []struct {
+		message   string
+		generator func() error
+		expected  string
+		tracer    bool
+	}{
+		{
+			message: "nil",
+			generator: func() error {
+				return nil
+			},
+		}, {
+			message: "raw error",
+			generator: func() error {
+				return fmt.Errorf("raw")
+			},
+			expected: "raw",
+		}, {
+			message: "single error stack",
+			generator: func() error {
+				return errors.New("first error") //err single
+			},
+			expected: "$single$: first error",
+			tracer:   true,
+		}, {
+			message: "annotated error",
+			generator: func() error {
+				err := errors.New("first error")          //err annotated-0
+				return errors.Annotate(err, "annotation") //err annotated-1
+			},
+			expected: "" +
+				"$annotated-0$: first error\n" +
+				"$annotated-1$: annotation",
+			tracer: true,
+		}, {
+			message: "wrapped error",
+			generator: func() error {
+				err := errors.New("first error")                    //err wrapped-0
+				return errors.Wrap(err, newError("detailed error")) //err wrapped-1
+			},
+			expected: "" +
+				"$wrapped-0$: first error\n" +
+				"$wrapped-1$: detailed error",
+			tracer: true,
+		}, {
+			message: "annotated wrapped error",
+			generator: func() error {
+				err := errors.Errorf("first error")                  //err ann-wrap-0
+				err = errors.Wrap(err, fmt.Errorf("detailed error")) //err ann-wrap-1
+				return errors.Annotatef(err, "annotated")            //err ann-wrap-2
+			},
+			expected: "" +
+				"$ann-wrap-0$: first error\n" +
+				"$ann-wrap-1$: detailed error\n" +
+				"$ann-wrap-2$: annotated",
+			tracer: true,
+		}, {
+			message: "traced, and annotated",
+			generator: func() error {
+				err := errors.New("first error")           //err stack-0
+				err = errors.Trace(err)                    //err stack-1
+				err = errors.Annotate(err, "some context") //err stack-2
+				err = errors.Trace(err)                    //err stack-3
+				err = errors.Annotate(err, "more context") //err stack-4
+				return errors.Trace(err)                   //err stack-5
+			},
+			expected: "" +
+				"$stack-0$: first error\n" +
+				"$stack-1$: \n" +
+				"$stack-2$: some context\n" +
+				"$stack-3$: \n" +
+				"$stack-4$: more context\n" +
+				"$stack-5$: ",
+			tracer: true,
+		}, {
+			message: "uncomparable, wrapped with a value error",
+			generator: func() error {
+				err := newNonComparableError("first error")     //err mixed-0
+				err = errors.Trace(err)                         //err mixed-1
+				err = errors.Wrap(err, newError("value error")) //err mixed-2
+				err = errors.Maskf(err, "masked")               //err mixed-3
+				err = errors.Annotate(err, "more context")      //err mixed-4
+				return errors.Trace(err)                        //err mixed-5
+			},
+			expected: "" +
+				"first error\n" +
+				"$mixed-1$: \n" +
+				"$mixed-2$: value error\n" +
+				"$mixed-3$: masked\n" +
+				"$mixed-4$: more context\n" +
+				"$mixed-5$: ",
+			tracer: true,
+		},
+	} {
+		c.Logf("%v: %s", i, test.message)
+		err := test.generator()
+		expected := replaceLocations(test.expected)
+		stack := errors.ErrorStack(err)
+		ok := c.Check(stack, gc.Equals, expected)
+		if !ok {
+			c.Logf("%#v", err)
+		}
+		tracer, ok := err.(tracer)
+		c.Check(ok, gc.Equals, test.tracer)
+		if ok {
+			stackTrace := tracer.StackTrace()
+			c.Check(stackTrace, gc.DeepEquals, strings.Split(stack, "\n"))
+		}
+	}
+}

vendor/github.com/juju/errors/package_test.go

@@ -0,0 +1,95 @@
+// Copyright 2013, 2014 Canonical Ltd.
+// Licensed under the LGPLv3, see LICENCE file for details.
+
+package errors_test
+
+import (
+	"fmt"
+	"io/ioutil"
+	"strings"
+	"testing"
+
+	gc "gopkg.in/check.v1"
+
+	"github.com/juju/errors"
+)
+
+func Test(t *testing.T) {
+	gc.TestingT(t)
+}
+
+func checkDetails(c *gc.C, err error, details string) {
+	c.Assert(err, gc.NotNil)
+	expectedDetails := replaceLocations(details)
+	c.Assert(errors.Details(err), gc.Equals, expectedDetails)
+}
+
+func checkErr(c *gc.C, err, cause error, msg string, details string) {
+	c.Assert(err, gc.NotNil)
+	c.Assert(err.Error(), gc.Equals, msg)
+	c.Assert(errors.Cause(err), gc.Equals, cause)
+	expectedDetails := replaceLocations(details)
+	c.Assert(errors.Details(err), gc.Equals, expectedDetails)
+}
+
+func replaceLocations(line string) string {
+	result := ""
+	for {
+		i := strings.Index(line, "$")
+		if i == -1 {
+			break
+		}
+		result += line[0:i]
+		line = line[i+1:]
+		i = strings.Index(line, "$")
+		if i == -1 {
+			panic("no second $")
+		}
+		result += location(line[0:i]).String()
+		line = line[i+1:]
+	}
+	result += line
+	return result
+}
+
+func location(tag string) Location {
+	loc, ok := tagToLocation[tag]
+	if !ok {
+		panic(fmt.Sprintf("tag %q not found", tag))
+	}
+	return loc
+}
+
+type Location struct {
+	file string
+	line int
+}
+
+func (loc Location) String() string {
+	return fmt.Sprintf("%s:%d", loc.file, loc.line)
+}
+
+var tagToLocation = make(map[string]Location)
+
+func setLocationsForErrorTags(filename string) {
+	data, err := ioutil.ReadFile(filename)
+	if err != nil {
+		panic(err)
+	}
+	filename = "github.com/juju/errors/" + filename
+	lines := strings.Split(string(data), "\n")
+	for i, line := range lines {
+		if j := strings.Index(line, "//err "); j >= 0 {
+			tag := line[j+len("//err "):]
+			if _, found := tagToLocation[tag]; found {
+				panic(fmt.Sprintf("tag %q already processed previously", tag))
+			}
+			tagToLocation[tag] = Location{file: filename, line: i + 1}
+		}
+	}
+}
+
+func init() {
+	setLocationsForErrorTags("error_test.go")
+	setLocationsForErrorTags("functions_test.go")
+}

vendor/github.com/juju/errors/path.go

@@ -0,0 +1,35 @@
+// Copyright 2013, 2014 Canonical Ltd.
+// Licensed under the LGPLv3, see LICENCE file for details.
+
+package errors
+
+import (
+	"runtime"
+	"strings"
+)
+
+// prefixSize is used internally to trim the user specific path from the
+// front of the returned filenames from the runtime call stack.
+var prefixSize int
+
+// goPath is the deduced path based on the location of this file as compiled.
+var goPath string
+
+func init() {
+	_, file, _, ok := runtime.Caller(0)
+	if ok {
+		// We know that the end of the file should be:
+		// github.com/juju/errors/path.go
+		size := len(file)
+		suffix := len("github.com/juju/errors/path.go")
+		goPath = file[:size-suffix]
+		prefixSize = len(goPath)
+	}
+}
+
+func trimGoPath(filename string) string {
+	if strings.HasPrefix(filename, goPath) {
+		return filename[prefixSize:]
+	}
+	return filename
+}

vendor/github.com/juju/errors/path_test.go

@@ -0,0 +1,29 @@
+// Copyright 2013, 2014 Canonical Ltd.
+// Licensed under the LGPLv3, see LICENCE file for details.
+
+package errors_test
+
+import (
+	"path"
+
+	gc "gopkg.in/check.v1"
+
+	"github.com/juju/errors"
+)
+
+type pathSuite struct{}
+
+var _ = gc.Suite(&pathSuite{})
+
+func (*pathSuite) TestGoPathSet(c *gc.C) {
+	c.Assert(errors.GoPath(), gc.Not(gc.Equals), "")
+}
+
+func (*pathSuite) TestTrimGoPath(c *gc.C) {
+	relativeImport := "github.com/foo/bar/baz.go"
+	filename := path.Join(errors.GoPath(), relativeImport)
+	c.Assert(errors.TrimGoPath(filename), gc.Equals, relativeImport)
+
+	absoluteImport := "/usr/share/foo/bar/baz.go"
+	c.Assert(errors.TrimGoPath(absoluteImport), gc.Equals, absoluteImport)
+}