+1 This looks good to me.

In theory, this logic should really go with python itself, not a third-party lib. i.e., once built, a Python implementation will match particular tags -- having a third party lib keep track of that seems to be putting it in the wrong place.

In practice, there are only so many versions out there, and we're only trying to support some of them, so it's probably fine for it to be in pip (and it can be upgraded so much more easily there)

-CHB