title: Install older Version of Python on Mac via virtualenv
body: <p>I need to install a certain package, for which the developers suggest <code>Python 3.5</code>, since they don't support <code>3.7</code> yet.
  I am running <code>Mac OS Mojave 10.14.2</code> and my Python version is <code>3.7.1</code>.</p>
  
  <p>I have come across methods to switch between <code>Python 2.x</code> and <code>3.x</code> using <code>Virtualenv</code>, such as below:</p>
  
  <pre><code>virtualenv -p python2 myenv
  
  virtualenv -p python3 myenv
  </code></pre>
  
  <p>However, is it even possible to have a specific version of Python, that too one older than I have already installed on my system?</p>