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/appletrawmain.py b/Lib/plat-mac/appletrawmain.py
index 7fc51d8..c863486 100644
--- a/Lib/plat-mac/appletrawmain.py
+++ b/Lib/plat-mac/appletrawmain.py
@@ -6,7 +6,7 @@
 #
 
 from warnings import warnpy3k
-warnpy3k("In 3.x, the appletrawmain module is removed.")
+warnpy3k("In 3.x, the appletrawmain module is removed.", stacklevel=2)
 
 import argvemulator
 import os