title: use apt-get install python packages in .gitlab-ci.yml
body: <p>my <code>gitlab-ci.yml</code> I install python-pandas but I can't use it from python.</p>
  
  <pre><code>$ cat .gitlab-ci.yml
  image: python:2
  
  test:
    script:
    - apt-get update -qy
    - apt-get install -y python-pip python-pandas
    - ls /usr/local/lib/python2.7/site-packages
    - python -c 'import pandas'
  </code></pre>
  
  <p>The runner failed with this message::</p>
  
  <pre><code> $ python -c 'import pandas'
    Traceback (most recent call last):
      File "&lt;string&gt;", line 1, in &lt;module&gt;
    ImportError: No module named pandas
    ERROR: Build failed: exit code 1
  </code></pre>
  
  <p>I try to not install pandas with pip as requirement (old pandas lib is enought)
  And very much would like to understand why python packages are not exposed ? this look like an implicit virtualenv !?</p>