title: `UnencryptedCookieSessionFactoryConfig` error when importing Apex
body: <p>I'm trying to use Apex and whenever I try to import it (or anything involving it) I get the following traceback:</p>
  <pre><code>Traceback (most recent call last):
    File &quot;&lt;stdin&gt;&quot;, line 1, in &lt;module&gt;
    File &quot;/home/user/anaconda3/lib/python3.8/site-packages/apex/__init__.py&quot;, line 13, in &lt;module&gt;
      from pyramid.session import UnencryptedCookieSessionFactoryConfig
  ImportError: cannot import name 'UnencryptedCookieSessionFactoryConfig' from 'pyramid.session' (unknown location)
  </code></pre>
  <p>I have the Pyramid library installed and importing that causes no issues. My Python version is 3.8.5 and my OS is Ubuntu 18.04.5.</p>
  <p>I've tried searching online but haven't been able to find a satisfactory solution and was hoping to know if anyone who is familiar would be able to provide some tips on what the problem may be and what I can do. Thanks.</p>