AttributeError: 'Connection' object has no attribute 'server_version'
Thanks for the quick report. This should be fixed -- I had been testing against pymysql and neglected to handle `MySQLdb` correctly.

I've pushed 3.9.1 which contains the fix.
Help! I got a problem when I call `create_tables` function with 3.90 version:

```
../../../.local/share/virtualenvs/shanbay_sea/lib/python3.6/site-packages/peewee.py:2989: in create_tables
    model.create_table(**options)
../../../.local/share/virtualenvs/shanbay_sea/lib/python3.6/site-packages/peewee.py:5999: in create_table
    and cls.table_exists():
../../../.local/share/virtualenvs/shanbay_sea/lib/python3.6/site-packages/peewee.py:5989: in table_exists
    return cls._schema.database.table_exists(M.table.__name__, M.schema)
../../../.local/share/virtualenvs/shanbay_sea/lib/python3.6/site-packages/peewee.py:2967: in table_exists
    return table_name in self.get_tables(schema=schema)
../../../.local/share/virtualenvs/shanbay_sea/lib/python3.6/site-packages/peewee.py:3620: in get_tables
    return [table for table, in self.execute_sql(query, ('VIEW',))]
../../../.local/share/virtualenvs/shanbay_sea/lib/python3.6/site-packages/peewee.py:2827: in execute_sql
    cursor = self.cursor(commit)
../../../.local/share/virtualenvs/shanbay_sea/lib/python3.6/site-packages/peewee.py:2813: in cursor
    self.connect()
../../../.local/share/virtualenvs/shanbay_sea/lib/python3.6/site-packages/playhouse/pool.py:108: in connect
    return super(PooledDatabase, self).connect(reuse_if_open)
../../../.local/share/virtualenvs/shanbay_sea/lib/python3.6/site-packages/peewee.py:2776: in connect
    self._state.set_connection(self._connect())
../../../.local/share/virtualenvs/shanbay_sea/lib/python3.6/site-packages/playhouse/pool.py:155: in _connect
    conn = super(PooledDatabase, self)._connect()
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _

self = <playhouse.pool.PooledMySQLDatabase object at 0x1079802e8>

    def _connect(self):
        if mysql is None:
            raise ImproperlyConfigured('MySQL driver not installed!')
        conn = mysql.connect(db=self.database, **self.connect_params)
        if self._server_version is None:
>           version_raw = conn.server_version
E           AttributeError: 'Connection' object has no attribute 'server_version'

conn       = <_mysql.connection open to 'mysql' at 0x7fbddbb4fc18>
self       = <playhouse.pool.PooledMySQLDatabase object at 0x1079802e8>
```

Are there some broken changes?