getattr-once.patch handles my first two points. It backports the set() change, and avoids the hasattr() check. I guess we apply this to 3.4+; expect merge conflicts with 3.6.

As for the last point, I will make another patch to include special attributes that don’t actually exist yet, where they are currently omitted. Would we consider this a new feature for 3.6? Going by Serhiy’s logic in <https://bugs.python.org/issue25209#msg251514> I would say yes.