Fixed #23620 -- Used more specific assertions in the Django test suite.
Fixed #18523 -- Added stream-like API to HttpResponse.

Added getvalue() to HttpResponse to return the content of the response,
along with a few other methods to partially match io.IOBase.

Thanks Claude Paroz for the suggestion and Nick Sanford for review.
Refactored URLValidator tests by moving URLs to text files.
Fixed #21281 -- Made override_settings act at class level when used as a TestCase decorator.
Fixed spelling mistake in docs/ref/request-response.txt
Fixed #23300 -- Made assertTemplateUsed throw an error on responses not fetched using the test client.

Thanks zags for the report and bmispelon for the patch.
Changed docstrings in admindocs/utils to comply to PEP 257
Fixed #5405 -- Added admindocs support for reStructured text in model docstrings

Thanks elvard and gkmngrgn for work on the patch and Markus H. for review.
Fixed typos using https://github.com/vlajos/misspell_fixer
Fixed versionchanged indentation in docs/.
Added HStoreField.

Thanks to `django-hstore` for inspiration in some areas, and many people
for reviews.
Added a warning about nonexistent FK constraints when unmigrated apps depend on migrated ones.

Thanks NotSqrt for the report; refs #23741.
Fixed links to mysqlclient in database notes.
Fixed #13181 -- Added support for callable choices to forms.ChoiceField

Thanks vanschelven and expleo for the initial patch.
Removed unused import.
Added missing docs to DiscoverRunner for keepdb option; refs #20550.
Fix minor typo in documentation.
Fixed #23531 -- Added CommonMiddleware.response_redirect_class.
Updated six to 1.8.0.
Removed confusing paragraph from the docs.

This snippet wasn't particularly helpful as `add_error()` is described
in greater details in the following section.

Thanks Claude Paroz for the report.