title: ssl with self signed certificate using python
body: <p>I am trying to build a simple server in python using my self signed certificate.
  I created .cer, .pfx, .pvk files using makecert.</p>
  
  <pre><code>context = ssl.create_default_context(ssl.Purpose.CLIENT_AUTH)
  context.load_cert_chain(certfile="ServerSSL.cer")
  
  Traceback (most recent call last):
    File "ssl_server.py", line 4, in &lt;module&gt;
      context.load_cert_chain(certfile="ServerSSL.cer")
  ssl.SSLError: [SSL] PEM lib (_ssl.c:2580)
  </code></pre>
  
  <p>What I did wrong?
  I also tried to convert my cer file to pem by changing the suffix and I got the same error.</p>