Fixed documentation of disable_constraint_checking

The docstring and base implementation of disable_constraint_checking do not indicate that a return value is expected for proper behavior.
Added clarification to the docs, pointing out that unique_for_date only considers the date portion of DateTime fields.
Fixed #20384 -- Forced GeoIP_open path argument to bytestring

Thanks Julian Wachholz for the report.
[py3] Made GeoIP tests pass with Python 3
Fixed #20385 -- Typo in files docs.
Fixed two admin_views tests under Oracle.

Thanks Anssi for the review.
Fixed an obvious typo.
Merge remote-tracking branch 'upstream/master'
Updated my bio.
Fixed #19939 -- generic relations + split_exclude regression

Added a test, the issue was already fixed (likely by the patch
for #19385).
Fixed #17365, #17366, #18727 -- Switched to discovery test runner.

Thanks to Preston Timmons for the bulk of the work on the patch, especially
updating Django's own test suite to comply with the requirements of the new
runner. Thanks also to Jannis Leidel and Mahdi Yusuf for earlier work on the
patch and the discovery runner.

Refs #11077, #17032, and #18670.
Update customizing.txt

The origin statement "which could be ... or whatever" **misguides** many newbies like me.

In fact, the ``login`` function in ``contrib.auth`` stores ``user.pk`` in session, then ``get_user`` function in ``contrib.auth`` gets ``user.pk`` in session and then passes it to your custom ``get_user`` as ``user_id``.

Which means, ``user_id`` prarameter in your custom ``get_user`` has to be the primary key of ``User`` object, too.
Fixed a regression in the test runner loading of runtests.py.

Refs #17365, #17366, #18727.
Properly force bytes or str for bcrypt on Python3
Fixed a regression from e23a5f9a4730ddecb8f3950ee2936716f458c506.

Excluded postgis specific gis tests from other spatial databases.

Refs #17365, #17366, #18727.
Merge pull request #1052 from dstufft/bcrypt-python3

BCrypt on Python3
Don't hardcode primary keys in gis tests.
Fixed embarrassing typo.
Fixed #20249 - Removed a "feature" in the tutorial that doesn't actually work.

Thanks bmispelon for the report and draft patch.
Fixed #20136 - Fixed and expanded the docs for loaddata and model signals.

Thanks brandon@ and Anssi for the report.