'Cannot delete content group if it is doesn\'t exist.'

def test_cannot_delete_non_existent_content_group(self):

    self._add_user_partitions(count=1, scheme_id='cohort')
    details_url_with_group_id = (self._url(cid=0) + '/90')
    response = self.client.delete(details_url_with_group_id, content_type='application/json', HTTP_ACCEPT='application/json', HTTP_X_REQUESTED_WITH='XMLHttpRequest')
    self.assertEqual(response.status_code, 404)
    user_partititons = self.course.user_partitions
    self.assertEqual(len(user_partititons), 1)
    self.assertEqual(len(user_partititons[0].groups), 3)
