Make plot helper compatible with Python 3.13

[brownbaerchen]

Python distutils has been deprecated since version 3.10 and removed in version 3.12. In 3.12 I could still use it but after switching to 3.13, the plot helper was broken for me. Apparently,distutil has been replaced by shutil. shutil.which returns what you get when you use which in the shell you run Python in, or None if there is no executable of the name you are looking for. Therefore, this should give the same functionality as distutil.spawn.find_executable as it is used in the plot helper.

[pancetta]

Any updates here?

[brownbaerchen]

This action also fails on the master branch of my fork. Not sure why it doesn't here. I am pretty sure that it is unrelated to the changes in this PR, but I'll try and change the way the test is launched later and see if it helps.

[tlunet]

Is the firedrake test the problematic one, of the Allen_Cahn ones ?

[brownbaerchen]

Is the firedrake test the problematic one, of the Allen_Cahn ones ?

The Allen_Cahn ones are just a one time whatever problem, I suppose. This one Firedrake test keeps failing.

[tlunet]

Does firedrake imports mpi4py or some MPI binding already on his side ? Got some problem with fenix once, where importing mpi4py before dolfin was producing an error in tests ...

[brownbaerchen]

Does firedrake imports mpi4py or some MPI binding already on his side ? Got some problem with fenix once, where importing mpi4py before dolfin was producing an error in tests ...

There are other tests using firedrake and mpi that run just fine. The failing one uses Firedrake ensemble communicators for space-time parallelism.

[pancetta]

Updates here?

[brownbaerchen]

Updates here?

I have not managed to fix the firedrake tests yet. This plotting stuff is not related, but I will try to fix the firedrake stuff, maybe this week, hopefully by the end of next week. No need to merge this before.