Fixes CMake version > 3.12 python-binding build failure

[CorbinFoucart]

My build (deal.II 9.3.3, Ubuntu 18.04) with python-bindings was failing at the cmake . stage. Looking at the CMakeLists.txt file and comparing against the CMake documentation, it seems that this is due to a deprecation of FindPythonInterp for newer versions of CMake.

In order to fix the issue, I added a check based on the User's CMake version, since deal.II supports older versions. Using the new CMake functionality sets different CMake variables for Python version, so I set the existing variables based on the new variables as well. They're needed later in the file.

After making these changes, I'm able to build the library, the quicktests pass, and I'm able to import the PyDealII python library from an interpreter.

[Rombur]

Looks good. Thanks for the PR.

[Rombur]

/rebuild

[peterrum]

@CorbinFoucart CI is not happy about your git name. Could you check the following page: https://github.com/dealii/dealii/wiki/Commit-authorship.

[Rombur]

@CorbinFoucart can you take a look @peterrum's comment. Let us know if you need any help.

[bangerth]

@CorbinFoucart Ping?

[CorbinFoucart]

Hi everyone, thanks for the ping. I will fix this in a day or so.

[CorbinFoucart]

I've amended the commit to include my full name. Is this fine, or should I open a new pull request?

When I run git log, I see

commit 0309955a9e381d66a82ac309bc8b151588380ea2 (HEAD -> python3_binding_cmake_build_fix, origin/python3_binding_cmake_build_fix)
Merge: 6ec688ec82 6d2b712476
Author: Corbin Foucart <corbin.foucart@gmail.com>
Date:   Sat May 7 15:55:36 2022 -0400

    Merge branch 'python3_binding_cmake_build_fix' of github.com:CorbinFoucart/dealii into python3_binding_cmake_build_fix

commit 6ec688ec82cc591a4869beb335c439bd88b3ef65
Author: Corbin Foucart <corbin.foucart@gmail.com>
Date:   Fri Apr 22 01:56:30 2022 -0400

    Fixes CMake version > 3.12 python-binding build failure due to deprecated FindPythonInterp call.

commit 6d2b712476e698aa61c5feef9898b5355a607525
Author: Corbin <corbin.foucart@gmail.com>
Date:   Fri Apr 22 01:56:30 2022 -0400

    Fixes CMake version > 3.12 python-binding build failure due to deprecated FindPythonInterp call.

commit 3efeff2bc1bde872b103867c2fa90ae5b7d80a5d (origin/master, origin/HEAD, master)
Merge: 4bbf721af4 3fcb617604
Author: David Wells <drwells@email.unc.edu>
Date:   Thu Apr 21 09:52:03 2022 -0400

    Merge pull request #13629 from kronbichler/fix_typos
    
    Fix typo in variable name

It looks like amending the commit created another commit, after which the author name is correct. However, it looks like the CI check still fails below.

[Rombur]

It looks like amending the commit created another commit, after which the author name is correct.

That's the problem. You will need to squash the two commits into one to fix that. Do you know how to do it? You can take a look at https://stackoverflow.com/a/5189600 After that you will need to use git push -f to force the push because you changed the history.

[Rombur]

Thanks for the patch @CorbinFoucart !