def _get_env_vars(self):
        """
        Return sanitized environment variables which will be used when launching
        a subprocess.

        :rtype: ``dict``
        """
        env_vars = {}

        if self._env:
            env_vars.update(self._env)

        # Remove "blacklisted" environment variables
        to_delete = []
        for key, value in env_vars.items():
            if key.lower() in BLACKLISTED_ENV_VARS:
                to_delete.append(key)

        for key in to_delete:
            LOG.debug(
                'User specified environment variable "%s" which is being ignored...'
                % (key)
            )
            del env_vars[key]

        return env_vars

        Return sanitized environment variables which will be used when launching
        a subprocess.

        :rtype: ``dict``
        
contrib/runners/python_runner/python_runner/python_runner.py