Several database backends struggle with binary data. This change
minimizes the risk of unrelated tests failures when binary fields
trigger errors.

Forward-port of 2e4bcb9b from stable/1.7.x.

This allows these tests to run on databases that reject duplicate NULL
values in unique fields e.g. SQL Server.

Forward port of 4fb50a9a from stable/1.7.x.

Thanks smeaton for report and Joël Rochat for spell check

Thanks django at patjack.co.uk.

Thanks peterbe for the report.

Thanks danielsamuels for the report

Thanks David Fischer for the report and Moayad Mardini for the
review.

Unicode method on model should return unicode

The example of a __unicode__ model method should return a unicode value
instead of a string.

Thanks Daniel Pope for the suggestion.

Thanks Rudolph for the report.

Removed the FieldError raised by ModelBase.__new__ in this case.

This reverts commit 9d1987d7.

Thanks Tim Graham for the report and Simon Charette for the review.

refs #19195.

Thanks to Trac alias tbartelmess for the report and the test project.

Fixed #20550 -- Added ability to preserve test db between runs

This reverts commit cb9c9a7b.

Note that the stdlib's version of pbkdf2_hmac will also be used in the upcoming Python 2.7.8 release

Thanks apollo13 for the review.

Thanks matklad for the report.

Fixed #22682 -- `makemigrations` will create `MIGRATION_MODULES` package

`makemigrations` will automatically create the package specified
in `MIGRATION_MODULES` if it doesn't already exist.

Thanks ovidiuc4 for the report.

Making SQL management commands migration aware.