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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
```

"""Error code for ansible-test matching the format used by the underlying test program, or None if the program does not use error codes."""
        return 'ansible-test'
    def filter_targets(self, targets):  
        """Return the given list of test targets, filtered to include only those relevant for the test."""
        return [target for target in targets if os.path.splitext(target.path)[1] == '.py' or is_subdir(target.path, 'bin')]
    def test(self, args, targets, python_version):
        """
        :type args: SanityConfig
        :type targets: SanityTargets
        :type python_version: str
        :rtype: TestResult
        """
        plugin_dir = os.path.join(SANITY_ROOT, 'pylint', 'plugins')
        plugin_names = sorted(p[0] for p in [
            os.path.splitext(p) for p in os.listdir(plugin_dir)] if p[1] == '.py' and p[0] != '__init__')
        settings = self.load_processor(args)
        paths = [target.path for target in targets.include]
        module_paths = [os.path.relpath(p, data_context().content.module_path).split(os.path.sep) for p in
                        paths if is_subdir(p, data_context().content.module_path)]
        module_dirs = sorted(set([p[0] for p in module_paths if len(p) > 1]))
        large_module_group_threshold = 500
        large_module_groups = [key for key, value in
                               itertools.groupby(module_paths, lambda p: p[0] if len(p) > 1 else '') if len(list(value)) > large_module_group_threshold]
        large_module_group_paths = [os.path.relpath(p, data_context().content.module_path).split(os.path.sep) for p in paths
                                    if any(is_subdir(p, os.path.join(data_context().content.module_path, g)) for g in large_module_groups)]
        large_module_group_dirs = sorted(set([os.path.sep.join(p[:2]) for p in large_module_group_paths if len(p) > 2]))
        contexts = []
        remaining_paths = set(paths)
        def add_context(available_paths, context_name, context_filter):