Assert pipelines check compatibility with Cython 0.X
We recently discovered an issue that the cython3 merge request introduced, breaking some of the code when running it with cython 0.X, see !201 (merged)
This is confusing, since the test IGWN pipeline uses cython 0.X, and it ran without issues. Possibly it is because it uses a finesse wheel build with cython3 and then runs it with cython 0.X, circumventing the issue.
If this is the case, we need to decide if we want to support users building finesse with cython 0.X, or only making sure our wheels install and run with cython 0.X.
We should first implement #604 (closed) and merge !200 (merged), since that changes the way finesse is built and how dependencies are defined.