...however, that doesn't give the correct result. The version
requirement is "use the latest version of all packages that work with
the Python version under test" and the changes I've suggested would mean
that on Python 2.6 and 2.7, the latest version of zope.interface
wouldn't be used.
What makes this even more "interesting" is that zope.interface isn't a
direct requirement of either of these projects, it's a dependency of a
dependency in both cases.