5.0.3 fails when git binary is not available

[sio]

Summary

Ansible-lint fails if git binary is not present on the machine. This is new behavior in 5.0.3, 5.0.2 was working fine.

Issue Type

• Bug Report

Ansible and Ansible Lint details

ansible 2.10.6
  config file = None
  configured module search path = ['/root/.ansible/plugins/modules', '/usr/share/ansible/plugins/modules']
  ansible python module location = /builds/sio/server_common/venv/lib/python3.7/site-packages/ansible
  executable location = /builds/sio/server_common/venv/bin/ansible
  python version = 3.7.3 (default, Jul 25 2020, 13:03:44) [GCC 8.3.0]

ansible-lint-5.0.3

• ansible installation method: pip
• ansible-lint installation method: pip

OS / ENVIRONMENT

Docker container based on debian:10-slim

STEPS TO REPRODUCE

Execute ansible-lint on a system where git is not installed.

Desired Behaviour

Ansible-lint works fine, except for the features that require VCS awareness like --progressive

Actual Behaviour

Ansible-lint throws an exception when it fails to locate git:

ansible-lint --exclude molecule -x yaml
Traceback (most recent call last):
  File "/builds/sio/server_common/venv/bin/ansible-lint", line 8, in <module>
    sys.exit(_run_cli_entrypoint())
  File "/builds/sio/server_common/venv/lib/python3.7/site-packages/ansiblelint/__main__.py", line 268, in _run_cli_entrypoint
    sys.exit(main(sys.argv))
  File "/builds/sio/server_common/venv/lib/python3.7/site-packages/ansiblelint/__main__.py", line 169, in main
    initialize_options(argv[1:])
  File "/builds/sio/server_common/venv/lib/python3.7/site-packages/ansiblelint/__main__.py", line 75, in initialize_options
    new_options = cli.get_config(arguments)
  File "/builds/sio/server_common/venv/lib/python3.7/site-packages/ansiblelint/cli.py", line 377, in get_config
    options.config_file or f"{guess_project_dir()}/.ansiblelint"
  File "/builds/sio/server_common/venv/lib/python3.7/site-packages/ansiblelint/file_utils.py", line 226, in guess_project_dir
    check=False,
  File "/usr/lib/python3.7/subprocess.py", line 472, in run
    with Popen(*popenargs, **kwargs) as process:
  File "/usr/lib/python3.7/subprocess.py", line 775, in __init__
    restore_signals, start_new_session)
  File "/usr/lib/python3.7/subprocess.py", line 1522, in _execute_child
    raise child_exception_type(errno_num, err_msg, err_filename)
FileNotFoundError: [Errno 2] No such file or directory: 'git': 'git'

Full log here: https://gitlab.com/sio/server_common/-/jobs/1088829855#L327