I've tried to add these lines to features/transcrits.py

{code}
import mock
from contentstore import transcripts_utils

# for mocking Youtube
@before.all
def set_mocked_youtube_api():
    world.youtube_api_patcher = mock.patch.dict(
        transcripts_utils.YOUTUBE_API,
        {'url': "http://127.0.0.1:" + str(settings.VIDEO_PORT) + '/test_transcripts_youtube/'}
    )
    world.youtube_api_patcher.start()
{code}