Compute coverage as part of CI/CD.

This MR is about adding coverage statistics' computation and reporting to our CI/CD pipelines.

It implements the following changes:

• Add 'pytest-cov' (hence, indirectly, 'coverage') to third-party dependencies of test environments.
• Add configuration of 'coverage' in 'pyproject.toml' to properly target declearn code (excluding protobuf-based code as well as the test_utils submodule) and be compatible with the use of multiprocessing in some functional~integration tests.
• Add coverage collection and xml reporting in 'tox.ini', notably via pytest instructions.
• Add 'coverage.xml' file to CI/CD pipelines' artifacts.
  • This should be sufficient to display coverage statistics via GitLab-provided tools of the repository.
  • In the future, it should be possible to extend the CI/CD configuration so that the coverage is exported to a GitLab Pages website, and possibly fetched back into our README so as to display a cool badge.

added automation label

assigned to @paandrey

added 1 commit

• 99a378d7 - Disable running 'test_routines.py' in CI/CD to avoid random failures.

Compare with previous version

As far as I can tell, the suggested configuration tweaks work. The integration to GitLab is still to be tested, but I am unsure whether it is achievable without merging to develop.

I disabled one of our functional tests. While its contents are covered by more advanced integration~functional tests, to me it underlines the need for writing proper unit tests for network communication endpoints. I will try to get around it next week (and open a dedicated MR), and the present MR may either be merged prior to or following it.

approved this merge request

added 46 commits

• 99a378d7...34779af9 - 43 commits from branch develop
• c8e04ad0 - Configure coverage tool with 'pyproject.toml'.
• a5eedd4a - Add coverage computation to 'tox.ini'.
• d6fe02b4 - Add coverage collection to GitLab CI/CD.

Compare with previous version

enabled an automatic merge when the pipeline for d6fe02b4 succeeds

merged

mentioned in commit 1bf6a11b