unknown error: row read wait bigger than connection timeout

More complicated queries result in a timeout:

```
engine.execute("SELECT o.symbol, coalesce(max(y.eod), '1900-01-06') - INTERVAL 5 DAY FROM optionable o LEFT OUTER JOIN yahoo y on y.symbol = o.symbol GROUP BY o.symbol")
```

result in:
```
Traceback (most recent call last):
File ".venv/lib/python3.7/site-packages/mysql/connector/connection_cext.py", line 489, in cmd_query
raw_as_string=raw_as_string)
_mysql_connector.MySQLInterfaceError: unknown error: row read wait bigger than connection timeout
```