python-livereload: watching changes raise "RuntimeError: Cannot close a running event loop"

.5/site-packages/apscheduler/executors/pool.py': 1526305704.9472704, '/home/yonghu/wode/myproject/regpark/venv/lib/python3.5/site-packages/flask/cli.py': 1526302662.0420418, '/usr/lib/python3.5/xml/etree/ElementTree.py': 1511887847.0, '/home/yonghu/wode/myproject/regpark/app/models.py': 1526395437.9710488, '/usr/lib/python3.5/asyncio/sslproto.py': 1511887846.0, '/home/yonghu/wode/myproject/regpark/venv/lib/python3.5/site-packages/jinja2/nodes.py': 1526302664.0981076, '/home/yonghu/wode/myproject/regpark/venv/lib/python3.5/site-packages/sqlalchemy/connectors/__init__.py': 1524256070.0})
Traceback (most recent call last):
  File "/home/yonghu/wode/myproject/regpark/venv/lib/python3.5/site-packages/tornado/ioloop.py", line 1208, in _run
    return self.callback()
  File "/home/yonghu/wode/myproject/regpark/venv/lib/python3.5/site-packages/tornado/autoreload.py", line 182, in _reload_on_update
    _check_file(modify_times, path)
  File "/home/yonghu/wode/myproject/regpark/venv/lib/python3.5/site-packages/tornado/autoreload.py", line 197, in _check_file
    _reload()
  File "/home/yonghu/wode/myproject/regpark/venv/lib/python3.5/site-packages/tornado/autoreload.py", line 204, in _reload
    fn()
  File "/home/yonghu/wode/myproject/regpark/venv/lib/python3.5/site-packages/livereload/server.py", line 310, in <lambda>
    add_reload_hook(lambda: IOLoop.instance().close(all_fds=True))
  File "/home/yonghu/wode/myproject/regpark/venv/lib/python3.5/site-packages/tornado/platform/asyncio.py", line 65, in close
    self.asyncio_loop.close()
  File "/usr/lib/python3.5/asyncio/unix_events.py", line 56, in close
    super().close()
  File "/usr/lib/python3.5/asyncio/selector_events.py", line 94, in close
    raise RuntimeError("Cannot close a running event loop")
RuntimeError: Cannot close a running event loop

--------------------------------above is error, follow is code------------------------------------------

@manager.command
def dev():
    from livereload import Server
    live_server = Server(app.wsgi_app)
    live_server.watch('**/*.*')
    live_server.serve(open_url=False)

the project is copied from another ubuntu computer, and is running correctly in another computer, almost everything is same between two computers, thanks for help