Clearer explanation when exception has no message

"No exception supplied" is misleading; actually there is an exception,
but there's no message string.
Fix #20505: Typo in BinaryField documentation.
Reimplemented PostGIS spatial_version with cached_property
Fixed #12491 -- Tweak checkbox widget help text alignment on the admin.

Thanks master' for the report and Niels van Dijk for the fix
Fixed #20507 -- SubqueryConstraint alias handling

MySQL should work now, too.
Fixed #17582 - Added message to DoesNotExist exceptions.

Thanks simon@ for the suggestion and JordanPowell
for the initial patch.
Merge pull request #1226 from bmispelon/ticket-20505

Fixed #20505 -- Typo in BinaryField documentation.
Fixed #16137 - Removed kwargs requirement for QuerySet.get_or_create

Thanks wilfred@, poirier, and charettes for work
on the patch.
Fixed #20501 -- failure of datetime queries with timezones under Oracle
Fixed #20013 -- A test for sqlall fails under Oracle
Fixed #11603 - Added django.test.SimpleTestCase.assertFormsetError

Thank-you Martin Green for the patch.
Fixed #20182 - admin lookup should treat 0 as False for __isnull

Thanks Benjie Chen.
Fixed #20014 -- implemented get_key_columns() for Oracle

Thanks Aymeric Augustin for reporting
Fixed #20503 - Moved doctest utilities in with the rest of the deprecated test code.

The ``DocTestRunner`` and ``OutputChecker`` were formerly in
``django.test.testcases``, now they are in ``django.test.simple``. This avoids
triggering the ``django.test._doctest`` deprecation message with any import
from ``django.test``. Since these utility classes are undocumented internal
API, they can be moved without a separate deprecation process.

Also removed the deprecation warnings specific to these classes, as they are
now covered by the module-level warning in ``django.test.simple``.

Thanks Anssi for the report.

Refs #17365.
Fixed random aggregation_regress test_more_more_more() failure

The cause was assuming that an unordered queryset returns the values
always in the same order.
Fixed #20513 - Expanded docs on QuerySet caching.

Thanks seddonym.
Fixed #20228 - Documented unique_for_date and exclude behavior.

Thanks Deepak Thukral for the patch.
Fixed #20523 - Incorrect form field for FilePathField.

Thanks sane4ka.sh@ for the report.
Fixed #20242 - Added a regression test for prefetch_related.

Issue was fixed by removal of chunked reads from
QuerySet iteration in 70679243d1786e03557c28929f9762a119e3ac14.

Thanks Simeon Visser for the patch.
Fixed #20484 -- Added model validation for GenericIPAddressField

GenericIPAddressField must not allow blank for NOT NULL fields

Thanks Erik Romijn.