fix: package version in nightly

The string returned by "make version" should not include the "-nightly"
suffix, otherwise tests fail.

Makefile

@@ -123,7 +123,7 @@ ci-bootstrap-images:
 ###### Additional commands
 
 version: ## Print the current tutor version
-	@python -c 'import io, os; about = {}; exec(io.open(os.path.join("tutor", "__about__.py"), "rt", encoding="utf-8").read(), about); print(about["__version__"])'
+	@python -c 'import io, os; about = {}; exec(io.open(os.path.join("tutor", "__about__.py"), "rt", encoding="utf-8").read(), about); print(about["__package_version__"])'
 
 ESCAPE = 
 help: ## Print this help

setup.py

@@ -40,7 +40,7 @@ ABOUT = load_about()
 
 setup(
     name="tutor",
-    version=ABOUT["__version__"].split("-")[0],  # drop "-nightly" suffix if present
+    version=ABOUT["__package_version__"],
     url="https://docs.tutor.overhang.io/",
     project_urls={
         "Documentation": "https://docs.tutor.overhang.io/",

tutor/__about__.py

@@ -18,6 +18,11 @@ __version_suffix__ = ""
 # name.
 __app__ = os.environ.get("TUTOR_APP", "tutor")
 
+# Package version, as installed by pip, does not include the version suffix.
+# Otherwise, nightly plugins will automatically install non-nightly Tutor
+# version.
+__package_version__ = __version__
+
 if __version_suffix__:
     __version__ += "-" + __version_suffix__
     __app__ += "-" + __version_suffix__