Cancel asynchronous iterator by timeout

I have a process running with asyncio which should run forever.

I can interact with that process with a ProcessIterator, which can (left out here) send data to stdin and fetch from stdout.

I can access the data with async for fd, data in ProcessIterator(...):.

The problem is now that the execution of this async iterator must be timelimited. If the time runs out, the timeout() function is called, but the exception does not originate out of the __anext__ function to notify of the timeout.

How can I raise this exception in the async iterator? I found no way of calling awaitable.throw(something) or similar for it.

class ProcessIterator:
    def __init__(self, process, loop, run_timeout):
        self.process = process
        self.loop = loop

        self.run_timeout = run_timeout

        # set the global timer
        self.overall_timer = self.loop.call_later(
            self.run_timeout, self.timeout)

    def timeout(self):
        # XXX: how do i pass this exception into the iterator?
        raise ProcTimeoutError(
            self.process.args,
            self.run_timeout,
            was_global,
        )

    async def __aiter__(self):
        return self

    async def __anext__(self):    
        if self.process.exited:
            raise StopAsyncIteration()

        else:
            # fetch output from the process asyncio.Queue()
            entry = await self.process.output_queue.get()
            if entry == StopIteration:
                raise StopAsyncIteration()

            return entry

The usage of the async iterator is now roughly:

async def test_coro(loop):
    code = 'print("rofl"); time.sleep(5); print("lol")'

    proc = Process([sys.executable, '-u', '-c', code])

    await proc.create()

    try:
        async for fd, line in ProcessIterator(proc, loop, run_timeout=1):
            print("%d: %s" % (fd, line))

    except ProcessTimeoutError as exc:
        # XXX This is the exception I'd like to get here! How can i throw it?
        print("timeout: %s" % exc)

    await proc.wait()

tl;dr: How can I throw a timed exception so it originates from a async iterator?