title: Pyreverse complaining even after having Graphviz
body: <p>I want to be able to save the output in PNG and have installed Graphviz. Still it complains saying Graphviz is not installed:</p>
  
  <blockquote>
    <p>The output format 'output.png' is currently not available. Please
    install 'Graphviz' to have other output formats than 'dot' or 'vcg'.</p>
  </blockquote>