Traceback (most recent call last):
  File "cusloop", line 16, in <module>
    run_timeout(loop, foo(loop), 3)
  File "cusloop", line 7, in run_timeout
    return loop.run_until_complete(timed_awaitable)
  File "/usr/lib/python3.6/asyncio/base_events.py", line 467, in run_until_complete
    return future.result()
  File "/usr/lib/python3.6/asyncio/tasks.py", line 358, in wait_for
    return fut.result()
  File "cusloop", line 10, in foo
    process = await create_subprocess_exec('sleep', '3', loop=loop)
  File "/usr/lib/python3.6/asyncio/subprocess.py", line 225, in create_subprocess_exec
    stderr=stderr, **kwds)
  File "/usr/lib/python3.6/asyncio/base_events.py", line 1191, in subprocess_exec
    bufsize, **kwargs)
  File "/usr/lib/python3.6/asyncio/unix_events.py", line 194, in _make_subprocess_transport
    self._child_watcher_callback, transp)
  File "/usr/lib/python3.6/asyncio/unix_events.py", line 858, in add_child_handler
    "Cannot add child handler, "
RuntimeError: Cannot add child handler, the child watcher does not have a loop attached