This is a small series of updates to fix Review Bot when running on

Review Board 5. Mostly, it involves using the upstream six instead of

Django's copy, which no longer exists in Django 3.2.
Usage is pretty minimal. Just one dictionary iteration and one

@python_2_unicode_compatible decorator (which six ships).

Along with other changes in this series, Review Bot now works on both

Review Board 4 and 5. Successfully configured Review Board, checked

worker status, and posted changes for review and saw that reviews were

performed.