Remove debugging print (not triggered by test suite) and add XXX comment about how the code should raise a SyntaxError.

Lib/compiler/transformer.py

@@ -811,8 +811,8 @@ class Transformer:
                 defaults.append(self.com_node(nodelist[i + 1]))
                 i = i + 2
             elif len(defaults):
+                # XXX This should be a syntax error.
                 # Treat "(a=1, b)" as "(a=1, b=None)"
-                print nodelist[i]
                 defaults.append(Const(None))
 
             i = i + 1