If the coroutine-iterator is going to raise RuntimeError rather than StopIteration, do you think the __await__() documentation <https://docs.python.org/dev/reference/datamodel.html#object.__await__> should be clarified?

IMO “yield from coroutine_iterator” might be plausable for some strange combination of 3.4 code and a 3.5 coroutine, but I think it would be rare. And if you added a check in __await__() then the using “await” wouldn’t need to rely on next() raising the RuntimeError.