Disable workaround for pickling as of Django 3.2.10

In fixing a completely unrelated regression, Django 3.2.10 (the minor
release) seems to have removed the need for our workaround for pickling
memoryviews. So make this an explicit check, and don't make the
conversion if not needed.

Final django 1.11 based version

This tag represents the final point where the codebase runs on Django
1.11. Starting from this, django 2.2 is the runtime.

To upgrade, one should first migrate to this tag and run all migrations.
When that is completed, switch to django 2.2 and continue migrating to
the latest version and run the migrations again (using django 2.2).

Final(?) python2 version

Add missing slash