Make git errors fatal when strict mode is active

[ssbarnea]

Fixes: #3062

[kpfleming]

Hmm... I can't reproduce the original problem using this branch, because the changes made for #2890 stop Git from generating the error I saw originally.

Instead I just 'broke' the repo clone so that Git would report errors when running ls-files. With that in place, using this branch and --strict, this is the result:

(lint-test-venv) kpfleming@balrog22:~/git-personal/ansible-systemd-networkd$ ansible-lint -v --strict
INFO     Set ANSIBLE_LIBRARY=/home/kpfleming/.cache/ansible-compat/988886/modules:/home/kpfleming/.ansible/plugins/modules:/usr/share/ansible/plugins/modules
INFO     Set ANSIBLE_COLLECTIONS_PATH=/home/kpfleming/.cache/ansible-compat/988886/collections:/home/kpfleming/.ansible/collections:/usr/share/ansible/collections
INFO     Set ANSIBLE_ROLES_PATH=/home/kpfleming/.cache/ansible-compat/988886/roles:/home/kpfleming/.ansible/roles:/usr/share/ansible/roles:/etc/ansible/roles
WARNING  Failed to discover lintable files using git: fatal: .git/index: index file open failed: Permission denied
Traceback (most recent call last):
  File "/home/kpfleming/git-personal/lint-test-venv/bin/ansible-lint", line 8, in <module>
    sys.exit(_run_cli_entrypoint())
             ^^^^^^^^^^^^^^^^^^^^^
  File "/home/kpfleming/git-personal/lint-test-venv/lib/python3.11/site-packages/ansiblelint/__main__.py", line 360, in _run_cli_entrypoint
    sys.exit(main(sys.argv))
             ^^^^^^^^^^^^^^
  File "/home/kpfleming/git-personal/lint-test-venv/lib/python3.11/site-packages/ansiblelint/__main__.py", line 250, in main
    result = _get_matches(rules, options)
             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/kpfleming/git-personal/lint-test-venv/lib/python3.11/site-packages/ansiblelint/runner.py", line 216, in _get_matches
    lintables = ansiblelint.utils.get_lintables(opts=options, args=options.lintables)
                ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/kpfleming/git-personal/lint-test-venv/lib/python3.11/site-packages/ansiblelint/utils.py", line 848, in get_lintables
    for filename in discover_lintables(opts):
                    ^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/kpfleming/git-personal/lint-test-venv/lib/python3.11/site-packages/ansiblelint/file_utils.py", line 420, in discover_lintables
    out_present = subprocess.check_output(
                  ^^^^^^^^^^^^^^^^^^^^^^^^
  File "/opt/python-3.11.2/lib/python3.11/subprocess.py", line 466, in check_output
    return run(*popenargs, stdout=PIPE, timeout=timeout, check=True,
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/opt/python-3.11.2/lib/python3.11/subprocess.py", line 571, in run
    raise CalledProcessError(retcode, process.args,
subprocess.CalledProcessError: Command '['git', '-c', 'safe.directory=/home/kpfleming/git-personal/ansible-systemd-networkd', 'ls-files', '--cached', '--others', '--exclude-standard', '-z']' returned non-zero exit status 128.

Without --strict ansible-lint falls back to the non-Git-based method of finding lintables, as expected.

[cidrblock]

Let's sys.exit(1) with a logger error and w/o a traceback