Enhance test suite - with inspiration from python container

[pvalena]

2. RHEL-8 with rails-ex ([log](https://gist.github.com/pvalena/b0a789cc87b158414af2d55be40a9ae8)) - rails-ex worked for me, with this branch: https://github.com/sclorg/rails-ex/tree/3.3 not sure where to configure this.
   _Also, there might be other failing tests, but It's not clear from the logs (they're not very readable)._

3. RHEL-9: same as RHEL-8.

@pvalena Regarding RHEL-8 and RHEL-9 you can take an inspiration from s2i-python-container like here: https://github.com/sclorg/s2i-python-container/blob/master/test/test-lib-python.sh#L95
Or create an issue for it, and I will fix it later on.

Originally posted by @phracek in #507 (comment)