Message 140730 - Python tracker

By this issue existing, that's the decision that we should probably do this, and I think the discussion shows we agree it should happen. How it's done is another way, and we have roughly a year to get it figured out before 3.3 gets closer.

I have a patch that implements this as a decorator, but it's out of date by now and not feature complete. It's on my todo list of patches to revive.