def METHOD_NAME(password_field, lookup_suffix):
    field_lookup = FieldLookupBackend()
    lookup = '__'.join(filter(None, [password_field, lookup_suffix]))
    with pytest.raises(PermissionDenied) as excinfo:
        field, new_lookup = field_lookup.get_field_from_lookup(Credential, lookup)
    assert 'not allowed' in str(excinfo.value)