[throwaway894345]

I don't think 100% compatibility should be a goal. The maintainers really need to step up and guide the community through a tough but important transition (reducing the API surface for C-extensions to some sane subset so the implementation can be optimized--see things like h.py) or Python will remain in its very slow local optimum while the world moves around it.

Yes, we just went through one "tough but important" transition (Python 2->3) and it sucks to have to do this so often, but it's the price we pay from making bad bets (in this case, unnecessarily exposing the entire CPython interpreter as the C-extension API surface on the assumption that it will never be necessary to make CPython faster because people who need speed will just write the slow parts in C).