I enquired generally whether there'd been any preliminary work on a port to Python 3 and Ralph suggested I raise a ticket . I slightly regret bringing up the subject ...
In the post, I mentioned that I was intending to take a quick look at the likely issues. This I have done, to the extent of making a /very/ heavy-handed port - the only install dependencies to survive are WebOb and (for Py2) simplejson. Of the testing dependencies, only nose, formencode, webtest and strainer remain.
"Ran 217 tests in 0.911s FAILED (SKIP=1, errors=29, failures=7)"
Management summary: so much blood on the carpet that there's a (weak) argument for a Py3-only version/rewrite. It's a moot point whether enough of tw2 would survive a Py3 port to be recognisable as the same package.
There's no WSGI as yet in PY3 (and even if one does eventually get adopted, I doubt that people will be in a rush to use it), so all the middleware WSGI and resource injection code becomes irrelevant.
Paste won't get ported, so the commands module becomes irrelevant.
Of the listed template engines, only Mako has a Py3 port
There are two specific dependencies that present significant issues:
formencode: allegedly, a port of formencode to Py3 is intended at some point (I used one I prepared earlier)
strainer: tests have an extensive dependency on strainer. Long-term, this would seem to require either a fork-and-port-to-py3 of strainer (I did enough to get it to work) or a comprehensive rewrite of the tw2core test suite.
I can make the bloody remains available but it's not for the squeamish. It /is/ feasible to maintain a both2and3 version of tw2core/tw2.forms but I'm not sure that it'll be perceived as desirable.
tox output attached for the benefit of the terminally curious.