### Summary

I know there is some ongoing work to mitigate these problems, but since I'm not aware which parts have already been addressed and which not, I want to share some common failures here which I've seen during the last days:

1. When running `ansible-test sanity --color -v --junit --coverage-check --changed --docker --base-branch origin/main --skip-test pylint --skip-test ansible-doc --skip-test validate-modules --allow-disabled` in CI, the Python 2.6 `import` test fails:
```
02:05 ERROR: Command "/root/ansible_collections/community/general/tests/output/.tmp/sanity/import/minimal-py26/bin/python /root/ansible/test/lib/ansible_test/_data/quiet_pip.py install --disable-pip-version-check coverage -c /root/ansible/test/lib/ansible_test/_data/requirements/constraints.txt" returned exit status 1.
02:05 >>> Standard Error
02:05 Could not find a version that satisfies the requirement coverage<5.0.0,>=4.5.1 (from -c /root/ansible/test/lib/ansible_test/_data/requirements/constraints.txt (line 2)) (from versions: )
02:05 No matching distribution found for coverage<5.0.0,>=4.5.1 (from -c /root/ansible/test/lib/ansible_test/_data/requirements/constraints.txt (line 2))
02:05 >>> Standard Output
02:05 Collecting coverage<5.0.0,>=4.5.1 (from -c /root/ansible/test/lib/ansible_test/_data/requirements/constraints.txt (line 2))
```
(See https://app.shippable.com/github/ansible-collections/community.general/runs/8257/1/console for the full log)

2. When running unit tests for Python 2.6 with `ansible-test units -v --color --docker --coverage` with `unittest2 ; python_version < '2.7'` in tests/unit/requirements.txt, it fails:
```
Run command: /usr/bin/python2.6 /root/ansible/test/lib/ansible_test/_data/quiet_pip.py install --disable-pip-version-check -r /root/ansible/test/lib/ansible_test/_data/requirements/units.txt -r tests/unit/requirements.txt coverage -c /root/ansible/test/lib/ansible_test/_data/requirements/constraints.txt
Collecting unittest2 (from -r tests/unit/requirements.txt (line 1))
  Could not find a version that satisfies the requirement unittest2 (from -r tests/unit/requirements.txt (line 1)) (from versions: )
No matching distribution found for unittest2 (from -r tests/unit/requirements.txt (line 1))
ERROR: Command "/usr/bin/python2.6 /root/ansible/test/lib/ansible_test/_data/quiet_pip.py install --disable-pip-version-check -r /root/ansible/test/lib/ansible_test/_data/requirements/units.txt -r tests/unit/requirements.txt coverage -c /root/ansible/test/lib/ansible_test/_data/requirements/constraints.txt" returned exit status 1.
```
(See https://github.com/ansible-collections/community.hrobot/runs/2264772861?check_suite_focus=true)


### Issue Type

Bug Report

### Component Name

ansible-test

### Ansible Version

```console (paste below)
devel
```


### Configuration

...

### OS / Environment

...

### Steps to Reproduce

...

### Expected Results

...

### Actual Results

...
add_lint(sanity)
    add_extra_docker_options(sanity, integration=False)
    shell = subparsers.add_parser('shell',
                                  parents=[common],
                                  help='open an interactive shell')
    shell.add_argument('--python',
                       metavar='VERSION',
                       choices=SUPPORTED_PYTHON_VERSIONS + ('default',),
                       help='python version: %s' % ', '.join(SUPPORTED_PYTHON_VERSIONS))
    shell.set_defaults(func=command_shell,
                       config=ShellConfig)
    shell.add_argument('--raw',
                       action='store_true',
                       help='direct to shell with no setup')
    add_environments(shell)
    add_extra_docker_options(shell)
    add_httptester_options(shell, argparse)
    coverage_common = argparse.ArgumentParser(add_help=False, parents=[common])
    add_environments(coverage_common, isolated_delegation=False)
    coverage = subparsers.add_parser('coverage',
                                     help='code coverage management and reporting')
    coverage_subparsers = coverage.add_subparsers(metavar='COMMAND')
    coverage_subparsers.required = True  
    add_coverage_analyze(coverage_subparsers, coverage_common)
    coverage_combine = coverage_subparsers.add_parser('combine',
                                                      parents=[coverage_common],
                                                      help='combine coverage data and rewrite remote paths')
    coverage_combine.set_defaults(func=command_coverage_combine,
                                  config=CoverageConfig)
    coverage_combine.add_argument('--export',