title: Python - Convert string representation of date to ISO 8601
body: <p>In Python, how can I convert a string like this:</p>
  
  <blockquote>
    <p>Thu, 16 Dec 2010 12:14:05 +0000</p>
  </blockquote>
  
  <p>to ISO 8601 format, while keeping the timezone?</p>
  
  <p>Please note that the orginal date is string, and the output should be string too, not <code>datetime</code> or something like that.</p>
  
  <p>I have no problem to use third parties libraries, though.</p>