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##### SUMMARY
ansible-test sanity --requirements fails to install pylint, which is needed.

##### ISSUE TYPE
- Bug Report

##### COMPONENT NAME
ansible-test

##### ANSIBLE VERSION
<!--- Paste verbatim output from "ansible --version" between quotes -->
```paste below
ansible 2.10.2
  config file = /Users/ssbarnea/.ansible.cfg
  configured module search path = ['/Users/ssbarnea/.ansible/plugins/modules', '/usr/share/ansible/plugins/modules']
  ansible python module location = /Users/ssbarnea/.pyenv/versions/3.9.0/lib/python3.9/site-packages/ansible
  executable location = /Users/ssbarnea/.pyenv/versions/3.9.0/bin/ansible
  python version = 3.9.0 (default, Oct 10 2020, 09:43:04) [Clang 11.0.0 (clang-1100.0.33.8)]
```

##### CONFIGURATION
<!--- Paste verbatim output from "ansible-config dump --only-changed" between quotes -->
```paste below

```

##### OS / ENVIRONMENT
<!--- Provide all relevant information below, e.g. target OS versions, network device firmware, etc. -->


##### STEPS TO REPRODUCE
<!--- Describe exactly how to reproduce the problem, using a minimal test-case -->

<!--- Paste example playbooks or commands between quotes below -->
```yaml

```

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##### EXPECTED RESULTS
Adding ``--requirements`` is supposed to install missing requirements, but fails to install pylint.

##### ACTUAL RESULTS
<!--- Describe what actually happened. If possible run with extra verbosity (-vvvv) -->

<!--- Paste verbatim command output between quotes -->
```paste below
See documentation for help: https://docs.ansible.com/ansible/2.10/dev_guide/testing/sanity/pep8.html
Running sanity test 'pslint'
Running sanity test 'pylint' with Python 3.9
ERROR: Command "/Users/ssbarnea/.pyenv/versions/3.9.0/bin/python3.9 -m pylint --jobs 0 --reports n --max-line-length 160 --max-complexity 20 --rcfile /Users/ssbarnea/.pyenv/versions/3.9.0/lib/python3.9/site-packages/ansible_test/_data/sanity/pylint/config/collection.cfg --output-format json --load-plugins string_format,blacklist,deprecated,pylint.extensions.mccabe tests/unit/test_example.py --collection-name pycontribs.protogen --collection-version 0.0.1" returned exit status 1.
>>> Standard Error
/Users/ssbarnea/.pyenv/versions/3.9.0/bin/python3.9: No module named pylint
```

for large_module_dir in large_module_group_dirs:
            add_context(remaining_paths, 'modules/%s' % large_module_dir, filter_path(os.path.join(data_context().content.module_path, large_module_dir)))
        for module_dir in module_dirs:
            add_context(remaining_paths, 'modules/%s' % module_dir, filter_path(os.path.join(data_context().content.module_path, module_dir)))
        add_context(remaining_paths, 'modules', filter_path(data_context().content.module_path))
        add_context(remaining_paths, 'module_utils', filter_path(data_context().content.module_utils_path))
        add_context(remaining_paths, 'units', filter_path(data_context().content.unit_path))
        if data_context().content.collection:
            add_context(remaining_paths, 'collection', lambda p: True)
        else:
            add_context(remaining_paths, 'validate-modules', filter_path('test/lib/ansible_test/_data/sanity/validate-modules/'))
            add_context(remaining_paths, 'validate-modules-unit', filter_path('test/lib/ansible_test/tests/validate-modules-unit/'))
            add_context(remaining_paths, 'sanity', filter_path('test/lib/ansible_test/_data/sanity/'))
            add_context(remaining_paths, 'ansible-test', filter_path('test/lib/'))
            add_context(remaining_paths, 'test', filter_path('test/'))
            add_context(remaining_paths, 'hacking', filter_path('hacking/'))
            add_context(remaining_paths, 'ansible', lambda p: True)
        messages = []
        context_times = []
        python = find_python(python_version)
        collection_detail = None
        if data_context().content.collection:
            try:
                collection_detail = get_collection_detail(args, python)
                if not collection_detail.version:
                    display.warning('Skipping pylint collection version checks since no collection version was found.')
            except CollectionDetailError as ex:
                display.warning('Skipping pylint collection version checks since collection detail loading failed: %s' % ex.reason)
        test_start = datetime.datetime.utcnow()
        for context, context_paths in sorted(contexts):