title: How to use python3 in virtual environment
body: <p>I want to create virtual environment using python3. But it takes python2 by default. I have both python2 and 3 installed on my machine.</p>
  
  <p>The ouput of when I create the virtual environment is:</p>
  
  <p><code>$ virtualenv .env
  Running virtualenv with interpreter /usr/bin/python2
  New python executable in /some/path/.env/bin/python2
  Also creating executable in /some/path/.env/bin/python
  Installing setuptools, pkg_resources, pip, wheel...done.</code></p>
  
  <p>I would like to specify which python version to use in the virtualenv.</p>