I'm a little confused. It looks like `root_path` returns option, so there's some failure modes to consider. On unix, I presume it'll never return `None` because `make_absolute` will work, but I don't understand the windows case at all.

If you have a volume-relative path, what's it relative to, if not the current directory? It could reference any file on the filesystem, but we opened the path from the OS and read the file so there's some path that it points to somewhere, riht?