AIFlow support python3.6

[jiangxin369]

Describe the feature

AIFlow support python3.6

Describe the solution you'd like

Describe alternatives you've considered

Additional context

When run aiflow with python3.6, notification server blocks wich following logs:

[2022-07-25 14:07:07,682 - server.py:68 [MainThread] - INFO: Notification server started.
[2022-07-25 14:07:18,780 - server.py:189 [Thread-1] - ERROR: Lock is not acquired.
Traceback (most recent call last):
  File "/root/venv_for_aiflow/lib64/python3.6/site-packages/notification_service/server.py", line 185, in _call_behavior_async
    return await behavior(argument, context), True
  File "/usr/lib64/python3.6/asyncio/coroutines.py", line 225, in coro
    res = yield from await_meth()
  File "/root/venv_for_aiflow/lib64/python3.6/site-packages/notification_service/service.py", line 221, in _list_all_events
    pass
  File "/usr/lib64/python3.6/asyncio/coroutines.py", line 212, in coro
    res = func(*args, **kw)
  File "/usr/lib64/python3.6/asyncio/locks.py", line 86, in __aexit__
    self.release()
  File "/usr/lib64/python3.6/asyncio/locks.py", line 207, in release
    raise RuntimeError('Lock is not acquired.')
RuntimeError: Lock is not acquired.