### 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

...
remote.add_argument('--remote-provider',
                        metavar='PROVIDER',
                        help='remote provider to use: %(choices)s',
                        choices=['default'] + sorted(AnsibleCoreCI.PROVIDERS.keys()),
                        default='default')
    remote.add_argument('--remote-endpoint',
                        metavar='ENDPOINT',
                        help='remote provisioning endpoint to use (default: auto)',
                        default=None)
    remote.add_argument('--remote-terminate',
                        metavar='WHEN',
                        help='terminate remote instance: %(choices)s (default: %(default)s)',
                        choices=['never', 'always', 'success'],
                        default='never')
def add_extra_coverage_options(parser):
    """
    :type parser: argparse.ArgumentParser
    """
    parser.add_argument('--group-by',
                        metavar='GROUP',
                        action='append',
                        choices=COVERAGE_GROUPS,
                        help='group output by: %s' % ', '.join(COVERAGE_GROUPS))
    parser.add_argument('--all',
                        action='store_true',
                        help='include all python/powershell source files')
    parser.add_argument('--stub',
                        action='store_true',
                        help='generate empty report of all python/powershell source files')
def add_httptester_options(parser, argparse):