title: pycharm doesn't see python3.7 interpreter
body: <p>I'm using Pycharm Community 2018.1.4 on Linux Mint 19 Tara Xfce.</p>
  
  <p>It works well with Python 3.5 interpreter.
  I installed Python 3.7 to be the default Python interpreter on the system.</p>
  
  <p><code>python -V</code> command returns <code>Python 3.7.0b3</code>
  I would like to use Python 3.7 in Pycharm.</p>
  
  <p>I've tried :</p>
  
  <pre><code>which python
  </code></pre>
  
  <p><code>/usr/bin/python</code></p>
  
  <pre><code>which python3.7
  </code></pre>
  
  <p><code>/usr/local/bin/python3.7</code></p>
  
  <p>When I go to <code>File &gt; Settings &gt; Project</code> and <code>Interpreter &gt; Add</code> and there is no <code>/usr/local</code> folder and there is no python3.7 in <code>/usr/bin</code></p>
  
  <p>I can <code>cd</code> to <code>/usr/local/bin</code> folder in the terminal, but Pycharm just can't.
  I restarted, uninstalled/reinstalled Pycharm, refreshed its inner browser, restarted my pc. Nothing changed.</p>
  
  <p>What am I missing?</p>