Message 159009 - Python tracker

No, it isn't. Changing the `IOError(errno.ENOENT, "...`s to `FileNotFoundError("...`s would half fix it.

The other half, the `OSError(errno.ENOSYS)`s, has a FIXME for what's the right error to raise in that case ("no application associated with files of this type"). I have no idea myself. None of the new PEP 3151 errors apply. Nor did any of the errnos strictly speaking AFAICT; ENOSYS was the closest approximation I could find. Thoughts? Custom error class? Different errno? Something else?