def get_subdirectory(cls, location):
        """
        Return the path to setup.py, relative to the repo root.
        Return None if setup.py is in the repo root.
        """
        # find the repo root
        repo_root = cls.run_command(
            ['root'], show_stdout=False, cwd=location).strip()
        if not os.path.isabs(repo_root):
            repo_root = os.path.abspath(os.path.join(location, repo_root))
        return find_path_to_setup_from_repo_root(location, repo_root)

        Return the path to setup.py, relative to the repo root.
        Return None if setup.py is in the repo root.
        
product/gradle-plugin/src/main/python/pip/_internal/vcs/mercurial.py