title: Mitm proxy with certificate pinned application
body: <p>I am trying to simulate MITM attack over signal's android messaging application. It's open source, so I put the <code>mitmproxy-ca-cert.pem</code> in android application for pinning and in the mobile trusted certificates too. I am still not getting any query to the server.
  Error at the client end is</p>
  
  <blockquote>
    <p>NonSuccessfulResponseCodeException: Bad response: 502 Bad Gateway</p>
  </blockquote>