Fixed test failures introduced in e716518ad29898fb25c820023aaf2fdd1c9eb4af

refs #20761
Fixed #20761 -- Reworded ForeignKey default error message
Fixed #10284 -- ModelFormSet.save(commit=False) no longer deletes objects

Thanks laureline.guerin@ and Wedg.
Fixed #20794 -- Documented changes to validate_email

4e2e8f39d changed the way validate_email behaves for foo@localhost
email addresses, but wasn't listed in the release notes.
Fixed #14300 -- Fixed initial SQL location if models is a package.

Thanks al_the_x for the report and fheinz for the draft patch.
Fixed typo in Custom management commands documentation.
Merge pull request #1395 from funkbit/master

Fixed typo in Custom management commands documentation.
Fixed #19941 -- Modified runtests.py to make running the tests easier.

1. Automatically use tests/../django as the Django version.
2. If settings aren't provided through --settings or DJANGO_SETTINGS_MODULE)
   then use test_sqlite.