Eh, better error message for the previous change.  It now says
"non-default argument follows default argument".
diff --git a/Python/compile.c b/Python/compile.c
index ef88eda..9871b0f 100644
--- a/Python/compile.c
+++ b/Python/compile.c
@@ -2724,7 +2724,7 @@
 			/* Treat "(a=1, b)" as an error */
 			if (ndefs)
 				com_error(c, PyExc_SyntaxError,
-					  "Missing parameter default value");
+			    "non-default argument follows default argument");
 		}
 		if (t != COMMA)
 			break;