Attached patch removes support for None from filter and
itertools.ifilter. My objections for removing that from map do not
apply because bool function can be used instead of None in filter
achieving similar performance and better clarity.
None support was apparently removed from map in r60206.
Remaining questions:
1. map(None,[]), filter(None,[]) and in fact map(anything,[]) still
work. I don't think that needs to be fixed.
2. Should None support be removed from itertools.ifilterfalse? I would
guess yes, unless it is going away.