[IO][NFC] Add helpful error message to assert
[IO][NFC] Add helpful error message to assert

root-mirror/root,root-mirror/root,root-mirror/root,root-mirror/root,root-mirror/root,root-mirror/root,olifre/root,root-mirror/root,olifre/root,olifre/root,root-mirror/root,root-mirror/root,olifre/root,olifre/root,olifre/root,olifre/root,olifre/root,olifre/root,root-mirror/root,root-mirror/root,olifre/root,olifre/root