`Fatal error on SSL transport` and `AttributeError: 'NoneType' object has no attribute 'feed_appdata'`

Hello, I tried running my strategy live today and got these errors repeating until 9:29:56AM at which point the Strategy's `stop` function was invoked. I'm not sure why this happened but I adjusted my cron job to wait until market opens before starting next time... maybe that will solve it? I'll have to wait until Monday to find out. In any case, here's my environment and the error messages:

I'm running this on a Raspberry Pi 3b running Raspbian with Python 3.6.2

```
09:27:17,ERROR,Fatal error on SSL transport
protocol:
transport: <_SelectorSocketTransport closing fd=19 read=idle write=>
Traceback (most recent call last):
File "/home/pi/Python-3.6.2/Lib/asyncio/sslproto.py", line 638, in _process_write_backlog
ssldata, offset = self._sslpipe.feed_appdata(data, offset)
AttributeError: 'NoneType' object has no attribute 'feed_appdata'
09:27:17,ERROR,error while consuming ws messages:
09:27:20,ERROR,Fatal error on SSL transport
```

Thanks!