* Updating Python Requirements

* Constrain django-cookies-samesite until dep bug fixed

* Fix PEP 8 problems revealed by pycodestyle upgrade

Co-authored-by: Tim McCormack <tmccormack@edx.org>
Co-authored-by: Jeremy Bowman <jbowman@edx.org>

This adds contraints to:
kiwisolver: next release only works with python>=3.6

The was run to upgrade:
django-splash
django-wiki
edx-search
The previous versions were constraining django below 2.0.

Co-authored-by: Robert Raposa <rraposa@edx.org>

Remove duplicate constraints in requirements/constraints.txt uncovered by the recent change in pip-compile output format. I sorted the pinned dependencies by name to try and make it more obvious if this happens again. I also upgraded to pip-tools 4.5.1, which removes the line numbers from the enhanced pip-compile output added in 4.5.0, which should reduce future diff churn and merge conflicts but means that there's a large diff this one last time.

Also unpin edx-search again after the previous change to do that was apparently broken by a merge conflict.

Some tests that used to mock the cache internals of ConfigurationModels
had to be modified to use CacheIsolationTestCase instead (the things
they were mocking no longer exist).

Removing the moto.

This is step 3 of DE-1824.

Also update:
* six 1.13.0 => 1.14.0
* edx-django-utils 2.0.2 => 2.0.3
* skip test that checks all model changes have migrations.  (We defer
  this to step 4.)

* Added pytest-json-report plugin
	- modifying app-opts in setup.cfg
	- adding hook to all conftest.py files in repo
	- setting report to be saved to test_root/log/warnings.json
	- Writing custom logic to save json report to avoid overwrite if pytest called twice
This was created to allow us to easily parse through test warnings in jenkins

* Switch make upgrade to Python 3.5

* bok-choy fixes, constrain django-debug-toolbar

* Remove flaky bok-choy test

Bump the version.

Upgraded xblock-google-drive to latest commit hash.

Some change in the requirements here may be responsible for increased
CPU and memory usage.  This is causing production LMS for edx.org to run
into lots of performance issues.  Reverting for now until we can narrow
it down to which change caused the issue.