aiomysql: SSCursor can't close while raise Error

if server send a error to SSCurosr, SSCursor try to call self._result._finish_unbuffered_query in close function

# SSCursor close funcion in  cursor.py line 604
if self._result is not None and self._result is conn._result:
    await self._result._finish_unbuffered_query()

but there is not a byte to read after recived a error packge, so the loop is allways waiting in the time, the error could’t raise out .

# _finish_unbuffered_query function in connection.py line 1197  
while self.unbuffered_active:
    packet = await self.connection._read_packet()

I met the bug after I seted a mysql variable

SET GLOBAL MAX_EXECUTION_TIME=3000

a SELECT statement will be aborted if it takes more than 3s.

the connection received a error package with erorno 3024, but the loop is waiting packge to finitshed unbuffered_query