title: Extract the value of a X.509 certificate custom extension using PyOpenSSL
body: <p>Using Python and PyOpenSSL, is there a way to retrieve the value of a custom extension? By custom extension, I mean an extension encoded using the arbitrary extension format described under ARBITRARY EXTENSIONS at <a href="http://www.openssl.org/docs/apps/x509v3_config.html" rel="nofollow">http://www.openssl.org/docs/apps/x509v3_config.html</a>.</p>
  
  <p>Also, is it possible to create a certificate that contains such an extension using PyOpenSSL?</p>
  
  <p>If the answer to either of these is "no", I would also be interested in pointers on how to do this with any other Python library. I do not want to perform system calls to the OpenSSL command line app.</p>