title: Graphviz's executables are not found (Python 3.4)
body: <p>I am running Python3.4 on Windows 7. I am trying to use the Python interface for graphviz. This is a script I intend to run:</p>
  
  <pre><code>from graphviz import Digraph
  import pydotplus
  
  dot = Digraph(comment='The Round Table')
  
  dot.node('A', 'King Arthur')
  dot.node('B', 'Sir Bedevere the Wise')
  dot.node('L', 'Sir Lancelot the Brave')
  dot.edges(['AB', 'AL'])
  dot.edge('B', 'L', constraint='false')
  
  print(dot.source)
  dot.render('test-output/round-table.gv', view=True)
  </code></pre>
  
  <p>I get the following error at runtime: </p>
  
  <pre><code>RuntimeError: failed to execute ['dot', '-Tpdf', '-O', 'test-output/round-table.gv'], make sure the Graphviz executables are on your systems' path
  </code></pre>
  
  <p>Now I am sure I have properly installed the correct dependencies. I first tried to set the correct environment variables. The graphviz executables are located at <strong>C:\Program Files (x86)\Graphviz2.37\bin</strong> so I went to the Environment Variables section. There are two sections there: User Variables and System Variables. Under System Variables I clicked on <strong>Path</strong> and then clicked <code>Edit</code> and added <strong>;C:\Program Files (x86)\Graphviz2.37\bin</strong> to the end of the string and saved. This didn't clear the error.</p>
  
  <p>Then, following the answer <a href="https://stackoverflow.com/questions/18438997/why-is-pydot-unable-to-find-graphvizs-executables-in-windows-8">given here</a> I uninstalled pydot (actually I use pydotplus here) and re-installed it again, but still no success. </p>
  
  <p>I have been trying for hours to fix this and the whole PATH variable thing is just confusing and frustrating.</p>