Fix some name errors in Mac modules.
diff --git a/Lib/plat-mac/macostools.py b/Lib/plat-mac/macostools.py
index 337cc7f..395001d 100644
--- a/Lib/plat-mac/macostools.py
+++ b/Lib/plat-mac/macostools.py
@@ -10,6 +10,7 @@
 from Carbon import Res
 from Carbon import File, Files
 import os
+import errno
 import MacOS
 try:
     openrf = MacOS.openrf