This facilitates other changes like refs #28160.

Missed in f7a363ee.

Refs #23879.

This reverts commit e0cc36f6.
The problem is the following:
  * With non-gis backends, gis_tests sub apps are not discovered
    (see runtests.py)
  * Consequently, the app_label is inferred from the gis_tests
    AppConfig
  * Then models with same names in different sub apps conflict
    because of same model_name/app_label pair.

refs #23395.

Used abstract inheritance to cut down on code repetition.

* Removed trailing whitespace.
* Added newline to EOF if missing.
* Removed blank lines at EOF.
* Removed some stray tabs.

Thanks geoffhing@gmail.com for the report.

Fixed #15378 -- Now properly handle OGR layers that have features with invalid geometries.  Thanks, kunitoki for bug report and initial patch.

git-svn-id: http://code.djangoproject.com/svn/django/trunk@15813 bcc190cf-cafb-0310-a4f2-bffc1f526a37

Fixed #12093 -- `LayerMapping` now takes into account model inheritance when looking for the geometry column; forgot to diable extent regression test on MySQL. 


git-svn-id: http://code.djangoproject.com/svn/django/trunk@11703 bcc190cf-cafb-0310-a4f2-bffc1f526a37

git-svn-id: http://code.djangoproject.com/svn/django/trunk@8219 bcc190cf-cafb-0310-a4f2-bffc1f526a37