Use `errno` instead, which is icky, but given that all of the failure modes are from POSIX I/O functions, it’s at least in keeping with them. This is a major API break. Signed-off-by: Philip Withnall <withnall@endlessm.com> Helps: #40
This would be nice to have more generally useful via filters in the allocations view. But for now, just make something simple work.
