For my own nefarious purposes of building Zope 2.7.0 from source with
/usr/pkg/bin/python2p3 (python23-pth-2.3.3nb2) I found the only
way I could get py-expat (in pkgsrc/textproc) to build to the
desired Python version was to edit pyversion.mk (in
usr/pkgsrc/lang/python):

PYTHON_VERSION_DEFAULT?=        23pth

...instead of '22'. 

How much trouble am I in? Is it ok to leave things that way?

-- 
Bob Bernstein

   "A modern philosopher who has never once suspected himself of
    being a charlatan must be such a shallow mind that his work is
    probably not worth reading."        Leszek Kolakowski