'Verify a validator checking non-existent courses.'

def test_validate_course_id_with_non_existent_course(self):

    course_key = 'non/existing/keyone'
    error_msg = u'Course    {}    does    not    exist.'.format(course_key)
    with self.assertRaisesRegexp(serializers.ValidationError, error_msg):
        validate_course_id(course_key)
