~~~~~~~~~~~~~~~~~~~~
* Dropping support for Python 2.7
* Switch to using edx-django-utils TieredCache (a two-layer cache that uses both
Django's cache and an internal request-level cache) to reduce the number of
memcached roundtrips. This was a major performance issue that accounted for
10-20% of transaction time for certain courseware views in edx-platform.
* It is now REQUIRED to add `RequestCacheMiddleware` `to middleware
<https://github.com/openedx/edx-django-utils/tree/master/edx_django_utils/cache#tieredcachemiddleware>`_
to use ConfigModels.
* Remove usage of the "configuration" cache setting. ConfigModels now always use
the default Django cache.
* Django Rest Framework 3.7 and 3.8 are no longer supported.