title: Exception: "dot" not found in path in python on mac
body: <p>I want to use <code>caffe.draw</code> to draw the caffe net by anaconda python on mac. But I got the error like this:</p>
  
  <pre><code>File "python/draw_net.py", line 45, in &lt;module&gt;
      main()
    File "python/draw_net.py", line 41, in main
      caffe.draw.draw_net_to_file(net, args.output_image_file, args.rankdir)
    File "/Users/xxh/caffe/distribute/python/caffe/draw.py", line 222, in draw_net_to_file
      fid.write(draw_net(caffe_net, rankdir, ext))
    File "/Users/xxh/caffe/distribute/python/caffe/draw.py", line 204, in draw_net
      return get_pydot_graph(caffe_net, rankdir).create(format=ext)
    File "/Users/xxh/anaconda2/lib/python2.7/site-packages/pydot.py", line 1883, in create
      prog=prog))
  Exception: "dot" not found in path.
  </code></pre>
  
  <p>I have installed pydot and graphviz ,and how can I add the dot's path to python path?</p>