This test doesn't pass on Windows.  The cause seems to be that chmod
doesn't support the same funcationality as on Unix.  I'm not sure if
this fix is the best (or if it will even work)--it's a test to see
if the buildbots start passing again.

It might be better to not even run this test if it's windows (or non-posix).
diff --git a/Lib/test/test_dumbdbm.py b/Lib/test/test_dumbdbm.py
index e5dfe1d..62fa3dd 100644
--- a/Lib/test/test_dumbdbm.py
+++ b/Lib/test/test_dumbdbm.py
@@ -50,11 +50,17 @@
         finally:
             os.umask(old_umask)
             
+        expected_mode = 0635
+        if os.name != 'posix':
+            # Windows only supports setting the read-only attribute.
+            # This shouldn't fail, but doesn't work like Unix either.
+            expected_mode = 0666
+
         import stat
         st = os.stat(_fname + '.dat')
-        self.assertEqual(stat.S_IMODE(st.st_mode), 0635)
+        self.assertEqual(stat.S_IMODE(st.st_mode), expected_mode)
         st = os.stat(_fname + '.dir')
-        self.assertEqual(stat.S_IMODE(st.st_mode), 0635)
+        self.assertEqual(stat.S_IMODE(st.st_mode), expected_mode)
         
     def test_close_twice(self):
         f = dumbdbm.open(_fname)