Why don't these apt-packages behave the same on Ubuntu and Heroku?

Question

I want to use ZBar from Python on Heroku. On a regular Ubuntu 14.04 server I can run either

sudo apt-get install python-qrtools

-- OR --

Answer 1

With the amazing help of @PadraicCunningham I managed to find the solution. The problem turned out to be that heroku-buildpack-apt installs things in a newly created folder /app/.apt/ which was not in the PYTHONPATH.

So I added the relevant folder to my PYTHONPATH on heroku as follows:

heroku config:add PYTHONPATH=/app/.apt/usr/lib/python2.7/dist-packages/

This solved the issue. Again a big thanks to PadraicCunningham for helping me to find this issue!