Add Python3 pre-commit config checks with pylint and mypy

[bernhardkaindl]

Updates:

• Add pyproject.toml with config for mypy, black and isort
• Enable spell checking when pre-commit runs pylint (uses pyenchant)
• tests/python/conftest.py: Add a pytest fixture for unit-tests
• tests/python/test_parse_test_instance_string.py: Add an initial unit test for xtf-runner using the pytest fixture.

Updated commit message:

Also enables spell checking when pre-commit runs pylint (uses pyenchant)

- Add pyproject.toml with config for mypy, black and isort
- Add .pre-commit-config.yaml for https://github.com/pre-commit
- Add GitHub action with cache to .github/workflows/build.yml
- Fix execute permissions on files found by pre-commit checks.
- build/mkinfo.py: Add module docstring as requested by pylint.
- tests/python/conftest.py: Add a pytest fixture for unit-tests
- tests/python/test_parse_test_instance_string.py: Add an
    initial unit test for xtf-runner using the pytest fixture.
- xtf-runner:
  - Import json always as Python2.7 is the minium version
  - Add comments to locally disable checks where needed.
  - Resolve a line-too-long while resolving a no-else-return

Signed-off-by: Bernhard Kaindl <bernhard.kaindl@cloud.com>
---
 .github/workflows/build.yml                   |  35 ++++++
 .pre-commit-config.yaml                       | 108 ++++++++++++++++++
 .pylintrc                                     |  40 ++++++-
 .pylintrc.project-dict.txt                    |  45 ++++++++
 build/mkcfg.py                                |   2 +-
 build/mkinfo.py                               |  35 +++++-
 include/xen/sysctl.h                          |   0
 tests/python/conftest.py                      |  53 +++++++++
 .../python/test_parse_test_instance_string.py |  34 ++++++
 xtf-runner                                    |  21 ++--
 10 files changed, 356 insertions(+), 17 deletions(-)
 create mode 100644 .pre-commit-config.yaml
 create mode 100644 .pylintrc.project-dict.txt
 mode change 100644 => 100755 build/mkcfg.py
 mode change 100644 => 100755 build/mkinfo.py
 mode change 100755 => 100644 include/xen/sysctl.h
 create mode 100644 tests/python/conftest.py
 create mode 100644 tests/python/test_parse_test_instance_string.py

---

This PR is ment as an example, but it may also be taken as-is or used as starting point for more:

Add Python3 pre-commit config checks with pylint and mypy:

• Add .pre-commit-config.yaml for https://github.com/pre-commit with a quick checks and automatic fixups:
  • The comments in it also include a brief introduction to using pre-commit: https://pre-commit.com/index.html#usage
• Add running the minimal https://pre-commit.com/ GitHub action with setup cache to .github/workflows/build.yml
• Update .pylintrc to also support passing the latest Python3 pylint checks while tolerating pylint config settings for old Python2-only pylint versions.
• Add the pylint-checked module docstring to build/mkinfo.py.
• The pre-commit checks also found that execute permissions on 3 files might be fixed, did so:
  • Changed the mode of the Python scripts which have shebangs: 100644 → 100755
  • include/xen/sysctl.h: 100755 → 100644
• xtf-runner:
  • Add type: ignore[no-redef] to for Python3 mypy and add a Python2-compatible type comment for mypy.
  • Add pylint: disable comments to locations where appropriate
  • Resolve a line-too-long warning while resolving a no-else-return pylint warning.

[bernhardkaindl]

Superseded by the devel branch and #8