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/macerrors.py b/Lib/plat-mac/macerrors.py
index 9629a0f..de1c1e2 100644
--- a/Lib/plat-mac/macerrors.py
+++ b/Lib/plat-mac/macerrors.py
@@ -1,7 +1,7 @@
 # -coding=latin1-
 
 from warnings import warnpy3k
-warnpy3k("In 3.x, the macerrors module is removed.")
+warnpy3k("In 3.x, the macerrors module is removed.", stacklevel=2)
 
 svTempDisable   =   -32768  #svTempDisable
 svDisabled  =   -32640  #Reserve range -32640 to -32768 for Apple temp disables.