In Python < 3.5, you could do a yield or yield None in a coroutine to give control to the event loop.
In Python 3.5, it is invalid to yield in an async def coroutine. So, what's the proper way of relinquishing control to the event loop?

One pattern is:

class AsyncNone(object):
    __await__(self):
        yield

async def cor():
    for _ in range(100):
        await AsyncNone()

But this seems very hacky.