title: Create a virtualenv with both python2 and python3
body: <p>I tried to use virtualenvwrapper to create a virtualenv with both python2 and python3</p>
  
  <p>Per <a href="https://stackoverflow.com/questions/12566064/virtualenv-with-python2-and-python3-via-homebrew">virtualenv with python2 and python3 via Homebrew</a> I hoped this would work:</p>
  
  <p>(The name of the virtualenv is 'double')</p>
  
  <pre><code>mkvirtualenv double -p `which python`
  mkvirtualenv double -p `which python3`
  </code></pre>
  
  <p>It mentions that </p>
  
  <pre><code>Not overwriting existing python script both/bin/python (you must use both/bin/python3.4)
  </code></pre>
  
  <p>But it that does not seem to be true. Typing <code>python</code> <code>python2.7</code> <code>python3</code> and <code>python3.4</code> all start the <code>python3.4</code> interpreter. </p>