Clean up expired sessions

[JensDiemer]

django doesn't clean up expired sessions. PyLucid should do this:

import datetime
from django.db import transaction
from django.contrib.sessions.models import Session

Session.objects.filter(expire_date__lt=datetime.datetime.now()).delete()
transaction.commit_unless_managed()

from:  http://code.djangoproject.com/browser/django/trunk/django/bin/daily_cleanup.py