title: Fedora 26 dnf update not working behind proxy
body: <p>On Fedora 26 when I do <code>sudo dnf update</code> I get the error </p>
  
  <blockquote>
    <p>Error: Failed to synchronize cache for repo 'updates'</p>
  </blockquote>
  
  <p>I configured both my system-wide proxy and the proxy in dnf.conf. Other connections such as the browser work with this proxy. </p>
  
  <p>How can I fix this?</p>