Replace imp module usage

[paulgessinger]

imp was removed in Python 3.12.

See #1194

BEGINRELEASENOTES

• Replace usage of the imp module that was removed in Python 3.12 with importlib and types.

ENDRELEASENOTES

[MarkusFrankATcernch]

@paulgessinger Thanks for helping in the maintenance!

[paulgessinger]

I think there might be a problem in lower python versions (from the CI output I wasn't sure what the test failures were exactly caused by). I'm trying to debug locally. The replacements I put in should be valid starting in python 3.4, so I don't think it's a fundamental error.

[MarkusFrankATcernch]

Let's see how the tests work out.
Otherwise we can still have a try...except approach trying one method and then the other...

[github-actions]

Test Results

       6 files         6 suites   6h 33m 15s ⏱️
   356 tests    356 ✔️ 0 💤 0 ❌
1 058 runs  1 058 ✔️ 0 💤 0 ❌

Results for commit 9f70625.

♻️ This comment has been updated with latest results.

[paulgessinger]

Hm, the pytest failures seem to be gone. There's now still two failures in ctest in g4units, but from a quick look they don't seem to be related to the python setup?

[MarkusFrankATcernch]

@paulgessinger Yes. The two problems should be unrelated. I restarted the failing test.
From the output it can also be that the Geant4 tracking setup and the generated track(s) are out of the phase space supported.