Fixing manager documentation inaccuracy
Removed 'return' in __init__
Merge pull request #2030 from frankwiles/master

Fixed manager documentation inaccuracy
Fixed a flake8 error
Fix poor variable name (flake8 warning)
Better error reporting when from_app_cache fails
Corrected setting name in gis test error message.
Fixed typo in custom model field documentation.
Fixed another typo in custom model field documentation.
Fixed #21562 -- Warned against using the same app name as a django contrib app.

Thanks yourcelf for the report.