title: python version conflict with json.dumps
body: <p>I am a newb to <code>python</code>. I am running a script I got on the web : </p>
  
  <pre><code>python file.py
  </code></pre>
  
  <p>I get this : </p>
  
  <pre><code>File "file.py", line 293
      print json.dumps(evaluate(), indent=4)
               ^
  SyntaxError: invalid syntax
  </code></pre>
  
  <p>I read it is related to python version, that should be some <code>2.7</code>. So I downloaded <code>pyenv</code>. And I set the right version in the directory that contains <code>file.py</code> : <code>pyenv local 2.7.10</code>. But I still get the same error. </p>
  
  <p>(For information, I am trying to install <code>blockchain</code> tool : ethereum)</p>