Actually for lettuce tests youtube stub server runs before every scenario. But in bok-choy we run youtube stub server once in the life time of tests and set/reset server configurations during the tests. So for lettuce the ```self.server.config['youtube_api_response'] = requests.get('http://www.youtube.com/iframe_api')``` is set everytime server runs but for bok-choy we set this value after every test completes. 
I think we don't need to set this value here. We can set this value once when server starts and  in ```do_DELETE``` delete all the ```keys``` except ```youtube_api_response```.