Google is now requiring an API key in order to access YouTube Data
web services.

To obtain a key:

1. Create a new project at https://console.developers.google.com/

2. Select newly created project, go to APIs & auth / APIs, select
   the Youtube Data API and enable api.

3. Go to APIs & auth / Credentials and create a new Public API
   access key ("Browser key").

4. If you are going to build minitube from ports, set
   MINITUBE_GOOGLE_API_KEY=your_key in make.conf. If you use package
   set GOOGLE_API_KEY environment variable to your key.