On http://pyxb.sourceforge.net/overview_how.html it looks like it says that Python 3.x is not supported at all, however in the changelog it says that it works for Python 3.x (x >=1).
Good catch; that part of the documentation wasn't updated. Python 3 support was added in PyXB 1.2.4, earlier than expected.
Ticket remains open until documentation updated in a released version.
close #36: document that Python 3 is supported as of 1.2.4