Implement Mark Favas's suggestion. There's a clear bug in _group():

its first return statement returns a single value while its caller
always expects it to return a tuple of two items.  Fix this by
returning (s, 0) instead.

This won't make the locale test on Irix succeed, but now it will fail
because of a bug in the platform's en_US locale rather than because of
a bug in the locale module.

Author: gvanrossum

Lib/locale.py

@@ -93,7 +93,7 @@ def strxfrm(s):
 def _group(s):
     conv=localeconv()
     grouping=conv['grouping']
-    if not grouping:return s
+    if not grouping:return (s, 0)
     result=""
     seps = 0
     spaces = ""