title: Python standard library to POST multipart/form-data encoded data
body: <p>I would like to POST multipart/form-data encoded data. 
  I have found an external module that does it: <a href="http://atlee.ca/software/poster/index.html" rel="noreferrer">http://atlee.ca/software/poster/index.html</a>
  however I would rather avoid this dependency. Is there a way to do this using the standard libraries?</p>
  
  <p>thanks</p>