title: ModuleNotFoundError: No module named 'markdown' when running lektor server
body: <p>When running lektor server to deploy and see my website, it reports markdown is absent, while it is installed.</p>
  <pre><code>/usr/local/lib/lektor/lib/python3.7/site-packages/watchdog/utils/bricks.py:175: DeprecationWarning: Using or importing the ABCs from 'collections' instead of from 'collections.abc' is deprecated, and in 3.8 it will stop working
  
    class OrderedSet(collections.MutableSet):
  Traceback (most recent call last):
  ...
  
    File &quot;/home/nick/swingrock.be/lektor/packages/tipue-content-file-generator/lektor_tipue_content_file_generator.py&quot;, line 7, in &lt;module&gt;
      import markdown
  
  ModuleNotFoundError: No module named 'markdown'
  </code></pre>
  <p>but markdown is installed, you can see the version here</p>
  <pre><code>nick@nick-VirtualBox:~/swingrock.be/lektor$ markdown --version
  
  This is Markdown, version 1.0.1.
  Copyright 2004 John Gruber
  http://daringfireball.net/projects/markdown/
  </code></pre>
  <p>Are there any steps I'm missing?</p>