The usual fixes except one oddity: the unit test that needed updating was using e.message to print data about an exception, and that was not working. e.message is not Python 3 compliant and my fix is, but the fact that e.message was apparently working before pybind11 suggests our exception wrappers may be missing a little something. On the other hand, this is a trivial update and I would prefer to modernize our code rather than add legacy support to our wrappers.

Pretty trivial indeed
One minor question on PR.

Question answered (and I kept the code as is). Thanks for the quick review. Merged.