[Catalog-sig] Python Version support in PyPI

[Monty Taylor]

Hey all,

OpenStack recently ran in to a problem where one of our depends released
a new version that only works with Python 3 and not Python 2. While I
wholeheartedly support the gusto of that, and also can't wait until we
can move to Python 3, there's a tooling issue here.

If I'm doing pip install pyparsing from python2, the system should have
enough information to be able to tell whether or not it's going to be
getting something that's just fundamentally incompatible - such as a
version that does not support python2.

I recognize that it would require the package in question marking itself
as not supporting python2 ... but let's face it, as we start doing this
py2-py3 transition in earnest, it's a pretty important piece of metadata
to know about - and I can't imagine we're going to be the only people
running in to the problem.

Anybody got any thoughts on ways we can help with this that won't suck?

Monty