Fails on Ubuntu Runners

Hey @coderpatros,

first of all, thanks for providing this action!

I came across the problem that this action fails on ubuntu.
[This repository](https://github.com/angrymeir/CycloneDX-test/actions/runs/515937271) executes the action for all available runners. As you can see it works on the other OS' perfectly.
Also when installing/running `cyclonedx-bom` on a local ubuntu it works fine for 18.04 and 20.04 (haven't tried 16.04).

I would be awesome if you could have a look at it :)