title: Can't send a request, OpenSSL key and cert error
body: <p>I have different error output for Linux and Windows (both use python 3.7.3 and PyOpenSSL 19.0).</p>
  
  <pre class="lang-py prettyprint-override"><code>
  response = s.post(url=my_url,
                   data=json.dumps(data.__dict__), 
                   timeout=15,
                   headers={'accept': 'application/json', 'content-type':'application/json'}, 
                   cert=(str(Path(__file__).parents[1]) + "/my_key.key",str(Path(__file__).parents[1]) + "/my_cert.crt"),
                   verify=False)
  </code></pre>
  
  <p>And I've installed <code>OpenSSL</code> and wrappers for Python on both systems.</p>
  
  <p>On Windows:
  <code>OpenSSL.SSL.Error: [('PEM routines', 'get_name', 'no start line'), ('SSL routines', 'use_certificate_chain_file', 'PEM lib')]</code></p>
  
  <p>On Linux 
  <code>[('PEM routines', 'get_name', 'no start line'), ('SSL routines', 'SSL_CTX_use_PrivateKey_file', 'PEM lib')]</code></p>
  
  <p>And I'm sure that cert and key are OK, because I've tried a <code>curl</code> request.</p>
  
  <p>What causes this error?</p>