Your example is looking like Data API v2..., the YouTube Data API v2.x has been officially deprecated as of March 4, 2014.
If you would like to make this work youtube Data API v3 is what you're looking for.
Some information and end of life message for YouTube API version 2 can be found here and YouTube Data API v3 docs can be found here if you're going to use the Data API v3 it should work again, don't forget to set the API key and make sure the status is ON for the YouTube Data API v3 in your developer account.
