title: Python 3.4 graphviz issue
body: <p>I have to run below code on Jupyter notebook. </p>
  
  <pre><code>from graphviz import Digraph
  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 have to install graphviz beforehand. after i installed graphviz 2.38 on windows 10. i did 'pip install graphviz'
  and 'conda install graphviz' as well. but i get this error </p>
  
  <p>"RuntimeError: failed to execute ['dot', '-Tsvg'], make sure the Graphviz executables are on your systems' path"</p>
  
  <p>What else should i do to make this error gone?</p>