Fixed #20594 -- Add validation to models.SlugField.

Thanks carbonXT for the report.
Fixed #20000 -- Allowed ModelForm meta overrides for label, help_text and error_messages
Added release notes for auth views being reversed by name, not by path.

Refs #20532
Added a ``checksetup`` management command for verifying Django compatibility.
Remove incorrect CONTENT_TYPE header from GET and HEAD requests
Merge pull request #1270 from tomchristie/remove-incorrect-content-type-test-client

Remove incorrect CONTENT_TYPE header from GET and HEAD requests
Fixed #17076 -- When reversing a URL fails, inform the user which patterns were tried.
Fixed #15273 -- Extend RedirectView to allow reversal by name.

Thanks to @DrMeers for the report and @ludwigkraatz for the initial patch.
Fixed #20598 -- Add new HTTP status codes defined in rfc6585

428, 429, 431 and 511
Fixed #20528 -- regression in select_related join promotion

The join used by select_related was incorrectly INNER when the query
had an ORed filter for nullable join that was trimmed away. Fixed this
by forcing the join type to LOUTER even when a join was trimmed away
in ORed queries.
Fixed python 3.2 compat.
Added cache to available_apps in cache tests
Fixed #20289 -- pickling of dynamic models
Fixed #20565 -- Added template examples for GCBV.

Thanks to David Reitter for the report,
and to Marc Tamlyn and Baptiste Mispelon for the review.
Fixed #20548 -- Removed all PendingDeprecationWarnings from django test suite
Merge pull request #1272 from chicheng/addition-http-status-codes

Fixed #20598 -- Add new HTTP status codes defined in rfc6585
Merge pull request #1271 from batisteo/ticket-20565

Fixed #20565 -- Added template examples for GCBV.
Fixed #20603 -- Made the test suite faster.

By avoiding to run syncdb with the full set of test models.

Thanks Anssi for the idea.
Added missing docs for the checksetup command.
Fixed #20604 - Fixed file example in docs.

Thanks Chris Lasher for the report.