title: Convert ISO 639-1 to ISO 639-2
body: <p>I need to take an <a href="https://en.wikipedia.org/w/index.php?title=Language_localisation&amp;oldid=685931772#Language_tags_and_codes" rel="nofollow noreferrer">ISO 639-1 code</a> such as <code>en-GB</code> and convert it into an <a href="https://en.wikipedia.org/wiki/ISO_639-2" rel="nofollow noreferrer">ISO 639-2 code</a> such as <code>eng</code>.</p>
  
  <p>I have looked at the following libraries, but did not find a documented means to perform that transformation in any of them:</p>
  
  <ul>
  <li><a href="https://pythonhosted.org/babelfish/" rel="nofollow noreferrer">BabelFish</a></li>
  <li><a href="https://github.com/LuminosoInsight/langcodes" rel="nofollow noreferrer">langcodes</a></li>
  <li><a href="https://pypi.python.org/pypi/pycountry" rel="nofollow noreferrer">pycountry</a></li>
  </ul>
  
  <p>Have I missed something? That is - is this possible with any of these libraries?</p>