Fixed #21212 -- Documented the reverse name for OneToOneField.

Thanks bjb at credil.org for the report.
Cleaned formatting/comments in PasswordResetFormTest
Fixed #21291 -- Ensured inactive users cannot reset their passwords

Thanks kz26 for the report and the suggested fix. Refs #19758.
Removed unused local variables in tests.
Fixed #21283 -- Added support for migrations if models is a package.

Thanks Markus Holtermann for the report.
Added support for serializing class methods. - Refs #21290.

The new handling allows us to do away with the whitelisting that was
required to support date and datetime objects.
Fixed an I18N test class tearDown method.
Fixed #21288 -- Fixed E126 pep8 warnings
Fixed E227 pep8 warnings
Removed some direct settings manipulations in tests; refs #21230.
Fixed #21296 -- Added docs for PostgreSQL and unix domains sockets.
Fixed #21253 -- PBKDF2 with cached HMAC key

This gives a 2x speed increase compared to the existing implementation.

Thanks to Steve Thomas for the initial patch and Tim Graham for finishing it.
Force update of the password on iteration count changes.
Added docs for the hasher's iteration count changes.
Fixed #21275 -- Fixed a serializer error when generating migrations for contrib.auth.

The migration serializer now looks for a deconstruct method on any object.
Fixed #21249 -- variable name typo in compiler.get_grouping()

The typo could have consequences in exceptional cases, but I didn't
figure out a way to actually produce such a case, so not tests.

Report & patch by Michael Manfre.
Fixed #19724 -- Output note when showing only core management commands

When listing available management commands, only core commands are
listed if settings have any error. This commit adds a note in this
case so errors are not totally silently skipped.
Thanks Peter Davis for the report.
Decode from UTF-8 explicitly when reading a text file in makemessages.

This shows itself with Python 3 under Windows where UTF-8 usually isn't
the default file I/O encoding and caused one failure and three errors
in our test suite under that platform setup.
Fixed indentation of example in tutuorial 2.
Removed import * in tests.

Thanks to flake8 path/to/file.py | awk -F ' ' '{ print $5 }' | sort | uniq