Add missing iteritems() call to the for loop in mailbox.MH.get_message().

Fixes issue2625.
diff --git a/Lib/mailbox.py b/Lib/mailbox.py
index 7651e53..7e0689c 100755
--- a/Lib/mailbox.py
+++ b/Lib/mailbox.py
@@ -911,7 +911,7 @@
                     _unlock_file(f)
         finally:
             f.close()
-        for name, key_list in self.get_sequences():
+        for name, key_list in self.get_sequences().iteritems():
             if key in key_list:
                 msg.add_sequence(name)
         return msg