    def test_check_unsafe_path(self):
        self.assertRaises(exception.Invalid,
                          disk_api._join_and_check_path_within_fs,
                          '/foo', 'etc/../../../something.conf')
The software uses external input to construct a pathname that is intended to identify a file or directory that is located underneath a restricted parent directory, but the software does not properly neutralize special elements within the pathname that can cause the pathname to resolve to a location that is outside of the restricted directory.