human
Solve the following python programming problem given the following code:
@ pytest.mark.django_db 
def test_backend_for_failed_auth(monkeypatch, django_user_model) : 
    '
    Test CAS authentication failure.
    ' 
    factory = RequestFactory () 
    request = factory.get ('/login/') 
    request.session = { 
        
} 
    def mock_verify(ticket, service) : 
        return (None, { 
            
}, None) 
monkeypatch.setattr ('cas.CASClientV2.verify_ticket', mock_verify) 
    assert (not django_user_model.objects.filter (username = 'test@example.com').exists ()) 
    backend = backends.CASBackend () 
    user = backend.authenticate (ticket = 'fake-ticket', service = 'fake-service', request = django_user_model) 
    assert (user is None) 
    assert (not django_user_model.objects.filter (username = 'test@example.com').exists ()) 

    
    

    Fix the buggy line: user = backend.authenticate (ticket = 'fake-ticket', service = 'fake-service', request = django_user_model)
assistant
#Here is Python code to fix the buggy line: user = backend.

user = backend.authenticate (ticket = 'fake-ticket', service = 'fake-service', request = request)