Improve the get_app compatibility method.
Review Request #10297 — Created Nov. 1, 2018 and submitted
This updates the
get_appcompatibility method to provide better
consistency between the behaviors of all supported versions of Django.
Error messages in the case of a missing models module is now consistent.
Documentation has also been updated to reflect the expected behavior.
Unit tests were added to ensure matching behavior across Django
Unit tests pass on all supported versions of Django.