#2503 make singletons compared with "is" not == or !=
Thanks to Wummel for the patch
diff --git a/Lib/test/test_mailbox.py b/Lib/test/test_mailbox.py
index 83802c1..7a12258 100644
--- a/Lib/test/test_mailbox.py
+++ b/Lib/test/test_mailbox.py
@@ -630,9 +630,9 @@
"tmp")),
"File in wrong location: '%s'" % head)
match = pattern.match(tail)
- self.assert_(match != None, "Invalid file name: '%s'" % tail)
+ self.assert_(match is not None, "Invalid file name: '%s'" % tail)
groups = match.groups()
- if previous_groups != None:
+ if previous_groups is not None:
self.assert_(int(groups[0] >= previous_groups[0]),
"Non-monotonic seconds: '%s' before '%s'" %
(previous_groups[0], groups[0]))