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
Fixed #5789 -- Changed LocaleMiddleware session variable to '_language'.

The old 'django_language' variable will still be read from in order
to migrate users. The backwards-compatability shim will be removed in
Django 1.8.

Thanks to jdunck for the report and stugots for the initial patch.
Fixed E221 pep8 warnings.
Fixed #17027 -- Added support for the power operator in F expressions.

Thanks dan at dlo.me for the initial patch.

- Added __pow__ and __rpow__ to ExpressionNode
- Added oracle and mysql specific power expressions
- Added used-defined power function for sqlite
Fixed #21304 -- Typo in docs/topics/testing/advanced.txt

Thanks joao at silvaneves.org for the report.
Added 1.5.5 and 1.4.9 release notes
Fixed #21307 -- Moved TransRealMixin to django.test.utils.
Fixed E225 pep8 warnings.
Workaround admin scripts test failures on Windows+Python 3.

Change strategy used to examine instrumented output to acommodate the
fact that on Windows, where the path separator is '\', repr() of Python
modules has changed in Python 3 to use escaped backslashes in the FS
path section (e.g.
'C:\\python3x\\Lib\\site-packages\\django\\contrib\\auth\\models.py')
without having to special-case based on platform.
Fixed #13245: Explained Oracle's behavior w.r.t db_table
and how to prevent table-name truncation

Thanks russellm & timo for discussion, and timo for review.