The comment is outdated, at this point, we should
really not get any errors from ReadDirIVAt.
The change is best seen when running the fsck tests. Before:
fsck: error opening dir "missing_diriv": 2=no such file or directory
After:
OpenDir "K2m0E6qzIfoLkVZJanoUiQ": could not read gocryptfs.diriv: no such file or directory
fsck: error opening dir "missing_diriv": 5=input/output error
See https://github.com/rfjakob/gocryptfs/issues/403 , where
the extra info would have been helpful.
e4148028af