Pyreverse complaining even after having Graphviz : <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>
