provides a clearer warning message when cheap inheritance with the underlying socket object is used

Lib/asyncore.py

@@ -407,8 +407,9 @@ class dispatcher:
             raise AttributeError("%s instance has no attribute '%s'"
                                  %(self.__class__.__name__, attr))
         else:
-            warnings.warn("cheap inheritance is deprecated", DeprecationWarning,
-                          stacklevel=2)
+            msg = "%(me)s.%(attr)s is deprecated. Use %(me)s.socket.%(attr)s " \
+                  "instead." % {'me': self.__class__.__name__, 'attr':attr}
+            warnings.warn(msg, DeprecationWarning, stacklevel=2)
             return retattr
 
     # log and log_info may be overridden to provide more sophisticated