Recent changes merged from Review Board 4 introduced usage of six to

modules that no longer used it. These have been switched to use

equivalent code for Python 3, and to fix some bad documentation that was

missed during development and review.
A recent unit test update for 5.0 was also broken. A raise was being

called in the else clause of a try/execpt, which isn't valid

(there's nothing to raise). This has been removed. Any exceptions will

just bubble up.

All unit tests pass (except for one that requires a larger update).