def get_default_cache():
    """
    Return the ``PYTHON_EGG_CACHE`` environment variable
    or a platform-relevant user cache dir for an app
    named "Python-Eggs".
    """
    return (
        os.environ.get('PYTHON_EGG_CACHE')
        or appdirs.user_cache_dir(appname='Python-Eggs')
    )

    Return the ``PYTHON_EGG_CACHE`` environment variable
    or a platform-relevant user cache dir for an app
    named "Python-Eggs".
    
src/pkg_resources/__init__.py