title: Python: lxml.etree.tostring(with_comments=False)
body: <p>I call the following command and get the following error:</p>
  
  <pre><code>&gt;&gt;&gt;lxml.etree.tostring([tree].getroot(), with_comments=False)
  ValueError: Can only discard comments in C14N serialisation
  </code></pre>
  
  <p>I don't know what C14N is, but I would appreciate an explanation of how I can achieve it and  run the foregoing command with <code>with_comments=False</code>.  (Yes, I'm aware that I can strip the comments using regex. Please don't offer regular expressions as a solution.)</p>
  
  <p><strong>Background:</strong> I want to transfer my xml doc over an http connection.  I'm using the lxml Python library.  I'm running on Python 2.7.1</p>