'Test CourseDescriptor.clean_id.'

def test_clean_id(self):

    self.assertEqual(self.course.clean_id(), 'course_ORSXG5C7N5ZGOL3UMVZXIX3DN52XE43FF52GK43UL5ZHK3Q=')
    self.assertEqual(self.course.clean_id(padding_char='$'), 'course_ORSXG5C7N5ZGOL3UMVZXIX3DN52XE43FF52GK43UL5ZHK3Q$')
