'Config: check_setting should raise on unknown'

@TestArgs('', 'This_IsNew_Name')
def test_check_setting_raise_on_unknown_settings(self, setting_name):

    path = '/tmp/notexist'
    exc_regex = re.compile(setting_name, re.IGNORECASE)
    c = headphones.config.Config(path)
    with self.assertRaisesRegexp(KeyError, exc_regex):
        c.check_setting(setting_name)
    pass
