title: Installed pytest but running `pytest` in bash returns `not found`
body: <p>I am following the <a href="https://pytest-django.readthedocs.io/en/latest/tutorial.html" rel="noreferrer">python-django</a> tutorial in Vagrant (Ubuntu 18.04 / Python3.6.6). After running <code>pip3 install pytest-django</code> and configuring <code>pytest.ini</code> file, running <code>pytest</code> returns</p>
  
  <pre><code>Command 'pytest' not found, but can be installed with:
  
  apt install python-pytest
  Please ask your administrator.
  </code></pre>
  
  <p><code>pip3 freeze</code> output:</p>
  
  <pre><code>pytest==3.10.0
  pytest-django==3.4.3
  </code></pre>
  
  <p>Is there something else to the installation?</p>