With the following directory structure:

    computer$ ls
    foo/
    computer$ ls foo/
    bar/  foo_file.txt
    computer$ ls foo/bar/
    bar_file.txt

Running:

    os.path.relpath('foo/bar/bar_file.txt', 'foo/foo_file.txt')

Returns:

    '../bar/bar_file.txt'

But should return:

    'bar/bar_file.txt'