I read the patch but I don't understand the logic behind it :-). Why should the value of tstate->exc_type affect whether we save/restore exc_info? Won't this mean that things are still broken for code like:

-----
def f():
    try:
        raise KeyError
    except Exception:
        try:
            yield
        except Exception:
            pass
        raise

try:
    raise NameError
except Exception:
    gen = f()
    gen.send(None)
    gen.throw(ValueError)
-----

?

Conceptually I would have thought the fix would be to remove the '!throwflag' check, but I haven't actually tried it...