See PEP 328[1] for details. This feature was introduced in Python 2.5 and
will become mandatory in Python 3.
[1]: http://www.python.org/dev/peps/pep-0328
(imported from commit 7444eeba8a08d5f91b94c7921848f2274979bd76)
The previous situation was bad for two reasons:
(1) It had a lot of copies of the code, some of them missing pieces:
UserProfile.objects.get(user__email__iexact=foo)
This was in particular going to be inconvenient since we are dropping
the __user part of that.
(2) It didn't take advantage of our memcached caching.
(imported from commit 2325795f288a7cf306cdae191f5d3080aac0651a)
We now clean up the stream subscription in more places, but some
historical tutorial streams are still around and if an error or page
reload happens during the tutorial it'll stick around.
(imported from commit 8cf0ebda26bf752c1a23296a4ba85d194bbb3004)
