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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
```

if not context_paths:
                continue
            context_start = datetime.datetime.utcnow()
            messages += self.pylint(args, context, context_paths, plugin_dir, plugin_names, python, collection_detail)
            context_end = datetime.datetime.utcnow()
            context_times.append('%s: %d (%s)' % (context, len(context_paths), context_end - context_start))
        test_end = datetime.datetime.utcnow()
        for context_time in context_times:
            display.info(context_time, verbosity=4)
        display.info('total: %d (%s)' % (len(paths), test_end - test_start), verbosity=4)
        errors = [SanityMessage(
            message=m['message'].replace('\n', ' '),
            path=m['path'],
            line=int(m['line']),
            column=int(m['column']),
            level=m['type'],
            code=m['symbol'],
        ) for m in messages]
        if args.explain:
            return SanitySuccess(self.name)
        errors = settings.process_errors(errors, paths)
        if errors:
            return SanityFailure(self.name, messages=errors)
        return SanitySuccess(self.name)
    @staticmethod
    def pylint(
            args,  
            context,  
            paths,  
            plugin_dir,