inc/python: Remove ability to mark packages as non-Python3

Everything in OpenStack *must* be Python 3 supporting now, which means
it's time to remove the functionality that allows us to blacklist
packages that didn't support Python 3.

Change-Id: I7c8cf538ec88bd4056b0109f19671e3d65f5da3a
Signed-off-by: Stephen Finucane <sfinucan@redhat.com>
3 files changed