'Verify that the command fails when the `to_mode` argument does not exist.'

def test_without_to_mode(self):

    self._enroll_users(self.course, self.users, 'audit')
    CourseModeFactory(course_id=self.course.id, mode_slug='audit')
    with self.assertRaises(CommandError):
        call_command('bulk_change_enrollment', course=unicode(self.course.id), from_mode='audit')
