Null value is eliminated by an aggregate or other SET operation

I am recieving this error
DatabaseError: Msg 8153, State 1, Line 1
Warning: Null value is eliminated by an aggregate or other SET operation.
which should be a warning

What is the recommended way to deal with this. If there is nothing 
preset, I believe there should be a connection-level list of errors to 
silently ignore (as in Subase.py:159)

def _servermsg_cb(ctx, conn, msg):
     # This is what should be configurable
     if msg.msgnumber not in (5701, 5703):
         raise DatabaseError(_fmt_server(msg))

¿Shouldn't I get a severity level for this warning?


Thanks
Marcos