Fixed #21243 -- Corrected exception message in multiple database tests.

Thanks to vajrasky for the report and patch.
Fixed regression introduced by 20472aa827669d2b83b74e521504e88e18d086a1.

The wrong exception was being caught when detecting the presence of GeoIP.
Thanks to ramiro for the report.
Fixed grammar/typos in auth customization docs
Fixed #19924 -- Fixed selectors in actions.js that did not use options.
Fixed #21222 - Documented that 'default' and 'other' must be different databases when running tests.

Thanks vernondcole for the suggestion.
Removed unnecessary semicolons.
Used "is" for comparisons with None.
Fixed "redefinition of unused 'foo' from line X" pyflakes warnings.
Fixed an undefined variable and clarified the purpose of a test.

refs #4459.
Whitespace cleanup.

* Removed trailing whitespace.
* Added newline to EOF if missing.
* Removed blank lines at EOF.
* Removed some stray tabs.
Sanitized test assertions in gdal tests
Small improvements to docs/topics/db/models.txt
Fixed assorted flake8 errors.
Fixed #8918 -- Made FileField.upload_to optional.

Thanks leahculver for the suggestion and dc and vajrasky for work
on the patch.
Fixed #13252 -- Added ability to serialize with natural primary keys.

Added ``--natural-foreign`` and ``--natural-primary`` options and
deprecated the ``--natural`` option to the ``dumpdata`` management
command.

Added ``use_natural_foreign_keys`` and ``use_natural_primary_keys``
arguments and deprecated the ``use_natural_keys`` argument to
``django.core.serializers.Serializer.serialize()``.

Thanks SmileyChris for the suggestion.
Added tests for URLValidator schemes.
Minor edits to docs/topics/db/queries.txt.
Fixed errors in 848101bf1736d1c01eb86968e85a14c7466bb376
Fixed #15582 -- Documented how TransactionTestCase.multi_db affects fixtures.

Thanks slinkp for the suggestion.