Some recent additions to Djblets broke compatibility with Python 3 and

with newer versions of Django. These breakages were pretty small, and

fortunately caught by unit tests (though there may be other breakages

not caught by tests).
This change fixes each of these, allowing tests to run again on all

supported Django 1.x releases and on both Python 2.7 and 3.5-3.7.

Unit tests pass on Django 1.6 and 1.11, with Python 2.7 and 3.5-3.7.