Currently, django.contrib.auth.views.login instantiates AuthenticationForm by passing it the request, which is optional; when this happens, AuthenticationForm will fail on valid logins unless set_test_cookie has been called previously. The login view itself does this, but this prevents easy reusability -- it's a fairly common use case to want to display a login box on each page for non-authenticated users, which means that each view in use must call set_test_cookie to ensure that the POST to login won't fail.
A simple solution to this would be to stop passing the request to AuthenticationForm. Perhaps a more flexible solution would be for login to begin taking a keyword argument to determine whether it should pass the request or not (and hence, whether set_test_cookie will be required or not)
