In the near term, we wish to precisely preserve the existing values of
all Django settings exposed by lms/envs/production.py in order to avoid
breaking legacy Django plugins without a proper announcement.
That includes preserving the behavior of these old, redundant dicts:
* ENV_TOKENS
* AUTH_TOKENS
* ENV_FEATURES
* ENV_CELERY_QUEUES
* ALTERNATE_QUEUE_ENVS
Particularly, it means we need to ensure that updates to Django
settings are reflected in these dicts. The most reliable way to do that
is to change the yaml-loading logic so that these values are aliased
to the corresponding values in the global namespace rather than
deep-copied.
Finally, we remove KEYS_WITH_MERGED_VALUES from the global namespace,
and inline the remaining list. We have modified the list (specifically,
we dropped the no-op MKTG_URL_OVERRIDES). Plugins should not be counting
on the value of the list, so we remove it.
0ea4bae7b3