Fix Python 3.12 CI

Fix #64 (closed)

A change in urllib means that relative paths now stay relative (https://github.com/python/cpython/issues/85110).

Ex: file.h5 resolves now to file:file.h5 instead of file:///file.h5. I fixed it by having the test changes depending on the Python version but perhaps we should do something more involved.

@denolf What do you think ? Do we expect changes for ewoks generally due to this ?