ARCH-193

18.0 seems to be doing a different thing with REMOTE_ADDR.

Putting this back to the last working version in production.

There is a breaking change in gunicorn 19 which changes
the behavior of the `REMOTE_ADDR` request meta info. It
no longer correctly passes through the value of X-Forwarded-For
if that header is present.

This resulted in making anything that looked at this attribute
think that all requests were coming from 127.0.0.1

This broke the django-ratelimit-backend library which relies on
this feature to determine if a user has had too many login attempts.

Gunicorn Change Log: http://docs.gunicorn.org/en/stable/2015-news.html

There are issues in the newest version that we don't want to pick up yet.

We're quite far behind, let's start by just looking at the treadmill.

There was an issue with migrations on sandboxes.

This reverts commit 58f6e925

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

This reverts commit 105db2cf, reversing
changes made to 44745759.

This also introduces a model for persisting organization-based filters on
a per-application basis. See openedx/core/djangoapps/oauth_dispatch/docs/decisions/0007-include-organizations-in-tokens.rst
for additional details.

This reverts commit 9a70ca78, reversing
changes made to efd5b9ab.

Hopefully fixes EDUCATOR-3053

It seems to have broken tests.

This reverts commit 18d93b00.

Reapplies edx/edx-platform#17509

This reverts commit 0f7e2373.

Update old transcripts metadata present in video xml with the new transcripts for backward compatibility.

added unit tests

updated edx-ace version

fixed quality violations

Fixed quality violations

Changed ACEMessageType to BaseMessageType

The published fork seems to be getting updates more regularly than the original project
and has the bugfix we forked for.

Use backoff when calling Sailthru API to retry upon optout timeouts.