core: Don't warn about Python 3 being experimental
core: Don't warn about Python 3 being experimental

We haven't had a Python 3 bug for a year.  There are probably more
lurking (like a halosaur), but Python 3 is the new normal.

MurphyMc/pox,MurphyMc/pox,MurphyMc/pox,MurphyMc/pox,MurphyMc/pox