Python: raise

[maximiliankaul]

Fixes #1710

[KuechA]

Not sure what's the intended order of the PRs. I made several comments on the parts in cpg-core in the PR #1733 which also apply here of course. The python-part looks straightforward but needs a test.

[maximiliankaul]

Not sure what's the intended order of the PRs. I made several comments on the parts in cpg-core in the PR #1733 which also apply here of course. The python-part looks straightforward but needs a test.

I want to have smaller, easier to review PRs:

1. We implement the general concepts in Implement a throw or raise statement #1733
2. We use them in all other languages. This PR being one of the required changes, after 1. is completed.