A friend and I have been working on porting gevent to py3:
It is about 90% completed - only about 60 tests are failing (out of some 1500). All of the "important" functionality - socket.py, ssl.py, server.py, pywsgi.py - seems to be in a good place.
Unfortunately, both of us are starting new jobs next week, and I'm not sure we can get it all the way in the near future. So we're looking for help! Please email me if you're interested, or, just pick a test and dive in. We forked the tests, so you should run the ones in "greentest-py3".