def login(request, *args, **kwargs):
    if request.method == 'POST':
        username = request.POST['username']
        uid = None
        try:
            user = User.objects.get(username = username)
            uid = user.id
        except ObjectDoesNotExist:
            pass
        if uid:
            sid = request.session.session_key
            duplicate_login = False
            sessions = Session.objects.all()
            for s in sessions:
                data = s.get_decoded()
                db_uid = -1
                db_sid = s.pk
                if data.has_key('_auth_user_id'):
                    db_uid = int(data['_auth_user_id'])
                    if uid == db_uid and sid != db_sid:
                        if datetime.now() < s.expire_date:
                            duplicate_login = True
            if duplicate_login:
                return render_to_response('duplicate_login.html',
                    context_instance = RequestContext(request))
    return auth_views.login(request, *args, **kwargs)