After looking over the things we expect to land in 1.13, I realized that none of them are really required for legacy users, so I've gone ahead and created a separate branch for py24 legacy systems (i.e. RHEL5).

This branch is client and builder only. Everything else has been removed.

Work on this branch will be as-needed, and it will be outside of our regular releases.

With that done, we can now target python 2.6+ on the master branch. This will allow us to speed up our py3 compatibility effort, and should ease some contributor pain.