Replace django-celery with django-celery-results
Upgrade redis to latest

Upgrade to 1.0.0 caused issues which are described and being
investigated in https://github.com/django-ses/django-ses/issues/186.

all versions updates were minor and no visible downgrades

This reverts commit f3161468.

- Updating Python Requirements
- Fix cache key generation to use class name and module

This was stringifying the class object directly, resulting in cache keys
like `:1:<class 'xblock_django.models.XBlockConfiguration'>.xblock_django.api.deprecated_xblocks`
which then cause breakage when Django 2.2.13 validates the keys.

Co-authored-by: edX requirements bot <testeng+edx-requirements-bot@edx.org>

Cleaned up a few more things about the testing configuration now that we've deployed Django 2.2 to production:

* Go back to a single version of django-oauth-toolkit, tox doesn't need to vary it anymore
* Go back to PyPI release of django-method-override
* Remove no longer needed dependency on python-oauth2 (we already removed the package it was used by)
* Update prepare_xdist_nodes.sh with new Django requirements file options

-Upgrade edx-drf-extensions
-settings-update

Remove DOP apps from INSTALLED_APPS.
Remove DOP libraries from requirements.

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.

- Reimplement `djcelery.common.respect_language` utility function so we
  can drop the dependency.
- Loosen `celery` pinning to a range, which brings in a fix for a
  possible crash bug

Also, pin `path` to 13.1.0 for now in order to continue supporting py35.

* Bumping edx-enterprise version

* Running make upgrade to bump edx-enterprise

* contraining a package

* fix

* adding yet another constraint

Django-auth-toolkit update

Pinned the latest commit from github to get Django2.2 support in testing.
Pinned the zipp<2.0.0 to get Python<3.5 support too.

Django 1.11 Changelog - https://docs.djangoproject.com/en/2.0/releases/1.11.14/

This reverts commit a7fa0c21.