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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
```

plugin_names,  
            python,  
            collection_detail,  
    ):  
        """Run pylint using the config specified by the context on the specified paths."""
        rcfile = os.path.join(SANITY_ROOT, 'pylint', 'config', context.split('/')[0] + '.cfg')
        if not os.path.exists(rcfile):
            if data_context().content.collection:
                rcfile = os.path.join(SANITY_ROOT, 'pylint', 'config', 'collection.cfg')
            else:
                rcfile = os.path.join(SANITY_ROOT, 'pylint', 'config', 'default.cfg')
        parser = ConfigParser()
        parser.read(rcfile)
        if parser.has_section('ansible-test'):
            config = dict(parser.items('ansible-test'))
        else:
            config = dict()
        disable_plugins = set(i.strip() for i in config.get('disable-plugins', '').split(',') if i)
        load_plugins = set(plugin_names + ['pylint.extensions.mccabe']) - disable_plugins
        cmd = [
            python,
            '-m', 'pylint',
            '--jobs', '0',
            '--reports', 'n',
            '--max-line-length', '160',
            '--max-complexity', '20',
            '--rcfile', rcfile,
            '--output-format', 'json',
            '--load-plugins', ','.join(load_plugins),
        ] + paths