title: graphviz in a virtual environment
body: <p>My project runs in a virtual environment with <code>Python 3.5</code> in Ubuntu 16.04. I want to visualize a graph output using <code>graphviz</code> (installed inside the virtual environment). But when I run the <code>render</code> function to visualize the graph, an error comes : </p>
  
  <pre><code>graphviz.backend.ExecutableNotFound: failed to execute ['dot', '-Tsvg', '-O', 'deBruijn.svg'], make sure the Graphviz executables are on your systems' PATH
  </code></pre>
  
  <p>How do I fix this issue by just modifying my virtual environment, without installing any package in the base OS (Ubuntu 16.04) ? </p>