Before we had : Requires-Python: 2.5, 2.6
That made much more sense. It was simple and unambiguous, and is relevant to typical packaging scenarios.
Unfortunately, it is fairly ambiguous, and makes no sense. It means "requires Python 2.5 *AND* requires Python 2.6", which is a requirement that no single version can meet.
No, it means a library requires either python 2.5 *OR* python 2.6 to be installed properly.
If Martin and the SIG disagree on the interpretation (and I see Martin's point: in ">=2.5, <2.6" the comma is a conjunction, not a disjunction), that's too much ambiguity for me.