* fix: check if editor is not found for `configure`
STD_EDITOR falls back on `vi` if $EDITOR and $VISUAL is not set.
However, some machines might not have `vi` symlinked or installed and a
bad error message is displayed. This commit adds a better error message.
* fix lint errors
* Change NotFound to write to stderr instead of panic!
Oh wow writing rust makes my commit messages look very enthusiastic!
