fix test_py3kwarns

The fact that this was failing and went unnoticed so long seems like a good argument for being able to enable and disble py3kwarnings through Python.
diff --git a/Lib/plat-mac/macresource.py b/Lib/plat-mac/macresource.py
index 0a66d76..f02453b 100644
--- a/Lib/plat-mac/macresource.py
+++ b/Lib/plat-mac/macresource.py
@@ -1,7 +1,7 @@
 """macresource - Locate and open the resources needed for a script."""
 
 from warnings import warnpy3k
-warnpy3k("In 3.x, the macresource module is removed.")
+warnpy3k("In 3.x, the macresource module is removed.", stacklevel=2)
 
 from Carbon import Res
 import os