Fix a handful of Python 3 and Django 1.11 compatibility issues.
Review Request #10510 — Created April 4, 2019 and submitted
This updates various miscellaneous pieces of code that were only
compatible with Python 2.7 and/or Django 1.6, making them compatible
with Python 3.x and Django 1.11.
There's fixes for importing of modules, string encodings, type checks,
generators vs. lists, Unicode characters in tests, model form
definitions, error messages that differed across versions, and other
Unit tests pass on Python 2.7/Django 1.6 and Python 3.7/Django 1.11
(with other in-progress changes).