Fix failing Windows checks

[fdiblen]

GitHub actions fail on Windows. We should fix it.
Related to #140

[sverhoeven]

Spend a lot of time trying to fixit, but gave up for now
Windows has been disabled in #241 . Failed attempts are #233 and #229

[jspaaks]

Not sure if this is caused by how we test the template or an different reason. If it is the former, I'm wondering if some of those difficulties go away if we don't try to run the template level's pytest to check the generated package?

For example, what if we have two virtual environments, one for the template, the other for the generated package? We could make 2 jobs out of it in one workflow.

[sverhoeven]

Creating a env on Windows is kaput just having following in GHA workflow:

    - name: venv
      run: python3 -m venv env

Fails with

Run python3 -m venv env
  python3 -m venv env
  shell: C:\Program Files\PowerShell\7\pwsh.EXE -command ". '{0}'"
  env:
    pythonLocation: C:\hostedtoolcache\windows\Python\3.9.4\x64
Error: [WinError 2] The system cannot find the file specified
Error: Process completed with exit code 1.

[sverhoeven]

Not sure if this is caused by how we test the template or an different reason. If it is the former, I'm wondering if some of those difficulties go away if we don't try to run the template level's pytest to check the generated package?

For example, what if we have two virtual environments, one for the template, the other for the generated package? We could make 2 jobs out of it in one workflow.

In #266 I am, only for Windows CI using the Python version created by actions/setup-python step instead of creating a new virtualenv.

[sverhoeven]

In #266 Windows test where fixed.