### 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

...
help='directory to export combined coverage files to')
    add_extra_coverage_options(coverage_combine)
    coverage_erase = coverage_subparsers.add_parser('erase',
                                                    parents=[coverage_common],
                                                    help='erase coverage data files')
    coverage_erase.set_defaults(func=command_coverage_erase,
                                config=CoverageConfig)
    coverage_report = coverage_subparsers.add_parser('report',
                                                     parents=[coverage_common],
                                                     help='generate console coverage report')
    coverage_report.set_defaults(func=command_coverage_report,
                                 config=CoverageReportConfig)
    coverage_report.add_argument('--show-missing',
                                 action='store_true',
                                 help='show line numbers of statements not executed')
    coverage_report.add_argument('--include',
                                 metavar='PAT1,PAT2,...',
                                 help='include only files whose paths match one of these '
                                      'patterns. Accepts shell-style wildcards, which must be '
                                      'quoted.')
    coverage_report.add_argument('--omit',
                                 metavar='PAT1,PAT2,...',
                                 help='omit files whose paths match one of these patterns. '
                                      'Accepts shell-style wildcards, which must be quoted.')
    add_extra_coverage_options(coverage_report)
    coverage_html = coverage_subparsers.add_parser('html',
                                                   parents=[coverage_common],
                                                   help='generate html coverage report')
    coverage_html.set_defaults(func=command_coverage_html,
                               config=CoverageConfig)