def get_paths_cfg(
    sys_file='pythran.cfg',
    platform_file='pythran-{}.cfg'.format(sys.platform),
    user_file='.pythranrc'
):
    """
    >>> os.environ['HOME'] = '/tmp/test'
    >>> get_paths_cfg()['user']
    '/tmp/test/.pythranrc'
    >>> os.environ['HOME'] = '/tmp/test'
    >>> os.environ['XDG_CONFIG_HOME'] = '/tmp/test2'
    >>> get_paths_cfg()['user']
    '/tmp/test2/.pythranrc'
    >>> os.environ['HOME'] = '/tmp/test'
    >>> os.environ['XDG_CONFIG_HOME'] = '/tmp/test2'
    >>> os.environ['PYTHRANRC'] = '/tmp/test3/pythranrc'
    >>> get_paths_cfg()['user']
    '/tmp/test3/pythranrc'
    """
    sys_config_dir = os.path.dirname(__file__)
    sys_config_path = os.path.join(sys_config_dir, sys_file)

    platform_config_path = os.path.join(sys_config_dir, platform_file)

    user_config_path = os.environ.get('PYTHRANRC', None)
    if not user_config_path:
        user_config_dir = os.environ.get('XDG_CONFIG_HOME', '~')
        user_config_path = os.path.expanduser(
            os.path.join(user_config_dir, user_file))
    return {"sys": sys_config_path, "platform": platform_config_path, "user": user_config_path}
>>> os.environ['HOME'] = '/tmp/test'
    >>> get_paths_cfg()['user']
    '/tmp/test/.pythranrc'
    >>> os.environ['HOME'] = '/tmp/test'
    >>> os.environ['XDG_CONFIG_HOME'] = '/tmp/test2'
    >>> get_paths_cfg()['user']
    '/tmp/test2/.pythranrc'
    >>> os.environ['HOME'] = '/tmp/test'
    >>> os.environ['XDG_CONFIG_HOME'] = '/tmp/test2'
    >>> os.environ['PYTHRANRC'] = '/tmp/test3/pythranrc'
    >>> get_paths_cfg()['user']
    '/tmp/test3/pythranrc'