This is for ticket #2501.
This is trivial and I did without review. I tested on two
systems (one with python3.3 and one without).

I didn't decide to make it open-ended at this time,
just in case we need to fix python3.4 issues first.

I decided not to add a changelog entry since was so trivial.
(Also had a workaround before by using --with-pythonpath.)