doc: http://cloud.youku.com/docs?id=46

def find_video_detail_by_id(self, video_id, ext=None):
        """doc: http://cloud.youku.com/docs?id=46
        """
        url = 'https://api.youku.com/videos/show.json'
        params = {
            'client_id': self.client_id,
            'video_id': video_id
        }
        if ext:
            params['ext'] = ext
        r = requests.get(url, params=params)
        check_error(r)
        return r.json()