pool is closed issue during unit test

[zillionare]

when performing unittest by tox, it complains:

tests/worker/test_jobs.py:23: 
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
/root/miniconda3/envs/omega/lib/python3.8/site-packages/omicron/__init__.py:32: in init
    await tf.init()
/root/miniconda3/envs/omega/lib/python3.8/site-packages/omicron/models/timeframe.py:113: in init
    await cls._load_calendar()
/root/miniconda3/envs/omega/lib/python3.8/site-packages/omicron/models/timeframe.py:103: in _load_calendar
    result = await cache.security.lrange(key, 0, -1)
/root/miniconda3/envs/omega/lib/python3.8/site-packages/aioredis/pool.py:257: in _wait_execute
    conn = await self.acquire(command, args)
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _

self = <ConnectionsPool [db:1, size:[1:10], free:0]>, command = b'LRANGE', args = ('calendar:1d', 0, -1)

    async def acquire(self, command=None, args=()):
        """Acquires a connection from free pool.
    
        Creates new connection if needed.
        """
        if self.closed:
>           raise PoolClosedError("Pool is closed")
E           aioredis.errors.PoolClosedError: Pool is closed

/root/miniconda3/envs/omega/lib/python3.8/site-packages/aioredis/pool.py:319: PoolClosedError

execute these ut case standalone contains no errors.