LOG里面出现这个错误

LINZING

2017-11-09 17:21:20 ERROR (Thread-14) [concurrent.futures] exception calling cal
lback for <Future at 0xa96aaa70 state=finished returned NoneType>
Traceback (most recent call last):
  File "/usr/lib/python3.5/concurrent/futures/_base.py", line 297, in _invoke_ca
llbacks
    callback(self)
  File "/usr/lib/python3.5/asyncio/futures.py", line 442, in _call_set_state
    dest_loop.call_soon_threadsafe(_set_state, destination, source)
  File "/usr/lib/python3.5/asyncio/base_events.py", line 532, in call_soon_threa
dsafe
    handle = self._call_soon(callback, args)
  File "/usr/lib/python3.5/asyncio/base_events.py", line 506, in _call_soon
    self._check_closed()
  File "/usr/lib/python3.5/asyncio/base_events.py", line 334, in _check_closed
    raise RuntimeError('Event loop is closed')
RuntimeError: Event loop is closed