diff -r 1bc0a8310b9f Lib/_osx_support.py
--- a/Lib/_osx_support.py	Thu Apr 17 20:11:19 2014 +0200
+++ b/Lib/_osx_support.py	Sat Apr 19 09:10:24 2014 -0400
@@ -68,7 +68,7 @@
 
     with contextlib.closing(fp) as fp:
         cmd = "%s 2>/dev/null >'%s'" % (commandstring, fp.name)
-        return fp.read().strip() if not os.system(cmd) else None
+        return fp.read().strip() if not os.system(cmd) else ''
 
 
 def _find_build_tool(toolname):