title: pygraphviz OSError: Format: "dot" not recognized. Use one of:
body: <p>I want to plot the tree generated by DEAP using pygraphviz. I tried to follow the example in this <a href="https://deap.readthedocs.io/en/master/tutorials/advanced/gp.html" rel="nofollow noreferrer">DEAP document</a>, but got the following error:</p>
  
  <pre><code>Traceback (most recent call last):
    File "&lt;input&gt;", line 24, in &lt;module&gt;
    File "C:\Users\xxyao\program\anaconda\envs\rf\lib\site-packages\pygraphviz\agraph.py", line 1399, in layout
      data = self._run_prog(prog, ' '.join([args, "-T", fmt]))
    File "C:\Users\xxyao\program\anaconda\envs\rf\lib\site-packages\pygraphviz\agraph.py", line 1364, in _run_prog
      raise IOError(b"".join(errors).decode(self.encoding))
  OSError: Format: "dot" not recognized. Use one of:
  </code></pre>
  
  <p>It seems like should be some words after the <code>Use one of:</code> but there is not. My environment is <code>Python==3.6</code>,<code>graphviz==3.41</code>,<code>pygraphviz==1.5</code>.The <code>graphviz</code>and <code>pygraphviz</code> are installed via <code>conda</code>.</p>
  
  <p>By the way,  I tried the following method: </p>
  
  <ol>
  <li>install graphviz and add <code>C:\Program Files (x86)\Graphviz2.38\bin</code> to system environment. </li>
  <li><code>conda install pydot</code>, <code>conda install pydot-ng</code> </li>
  </ol>
  
  <p>but it still doesn't work.</p>
  
  <p>Further infomation: Other layout provided by <code>pygraphviz</code> such as <code>neato fdp twopi</code> works well. Only the <code>dot</code> doesn't work!</p>