Py_None is what PyWeakref_GET_OBJECT() returns when the object is dead.
(same as calling () on a weakref, really)

The patch looks straightforward to me. 2.7 doesn't receive performance fixes, though, except for large regressions. Also, we've had enough regressions in the last 2.7 bugfix release, IMHO.

(I had worked on a patch which replaced the list with a dict, but I had refcounting issues with it, and I'm not interested enough in the issue to push any further)