Fix syntax for regexp group access

Mailman/Queue/LMTPRunner.py

@@ -286,7 +286,7 @@ class Channel(asynchat.async_chat):
         m = BATV_RX.match(address)
         if not m:
             return address
-        return m[1]
+        return m.group(1)
 
     # Implementation of base class abstract method
     def found_terminator(self):