ls: handle non-existing files correctly

Print an error message instead of just printing the file name
when the file does not exist.

Signed-off-by: Sasha Levin <levinsasha928@gmail.com>
Signed-off-by: Pekka Enberg <penberg@cloudius-systems.com>
md5sum: fix ugly spew when file doesn't exist

We'd get an ugly spew if the file doesn't exist. Replace it with
a much nicer message.

Signed-off-by: Sasha Levin <levinsasha928@gmail.com>
Signed-off-by: Pekka Enberg <penberg@cloudius-systems.com>