Fix codecov 0% issue by using pytest-cov

[bobleesj]

@Tieqiong

Can we try to implement the below change?

---

We shall use pytest-cov instead of using coverage to run pytest. The previous codecov 0% error occurred because the tests folder has been moved to the top directory level and coverage isn't able to import diffpy. due to the namespace.

So the GH actions can be modified

from:

        run: |
          coverage run -m pytest -vv -s
          coverage report -m
          codecov

to:

        run: |
          pytest --cov
          coverage report -m
          codecov

Reference:

• Create codecov.yml for coverage testing (Do not merge) diffpy/diffpy.snmf#86

Two more things to confirm with you:

I will also update .coveragerc to remove the source section.

Reference:

• https://github.com/diffpy/diffpy.snmf/pull/86/files

I will include pytest-cov in the test.txt dependency list.

[Tieqiong]

@bobleesj yes please make a PR in release-script

[bobleesj]

Got it. Once the PR is merged above, I will test whether it codecov % works using diffpy.utils and diffpy.snmf.

And then I will modify test.txt and .coveragerc in the overall cookiecutter.

[bobleesj]

Closes with scikit-package/scikit-package#155