Django has deprecated django.utils.timezone.utc in favor of

datetime.timezone.utc. The rest of the django.utils.timezone methods

are still supported. Furthermore, datetime.timezone.utc cannot be

directly imported, and must be accessed through datetime.timezone.
This leaves two possible importable targets named datetime (both

datetime and datetime.datetime) and named timezone

(datetime.timezone and django.utils.timezone), all of which are

relevant.
In an effort to keep things sane and consistent, the codebase now

imports the top-level datetime (accessing everything as a direct

property access of that) and django.utils.timezone as timezone in

all affected modules. We may opt to go this route with all new Django

code going forward.
With this change, all datetime-related warnings in unit tests have been

removed.

All unit tests pass.