SF patch 1631942 by Collin Winter:
(a) "except E, V" -> "except E as V"
(b) V is now limited to a simple name (local variable)
(c) V is now deleted at the end of the except block
diff --git a/Modules/parsermodule.c b/Modules/parsermodule.c
index d474a9a..d159b6b 100644
--- a/Modules/parsermodule.c
+++ b/Modules/parsermodule.c
@@ -2110,8 +2110,8 @@
     if (res && (nch > 1))
         res = validate_test(CHILD(tree, 1));
     if (res && (nch == 4))
-        res = (validate_comma(CHILD(tree, 2))
-               && validate_test(CHILD(tree, 3)));
+        res = (validate_name(CHILD(tree, 2), "as")
+               && validate_ntype(CHILD(tree, 3), NAME));
 
     return (res);
 }