when trying to mount a cifs share with sec=krb5 but with missing krb5 key, then the mount command returns:
mount error(2): No such file or directory
This error message does not really help most of the users, I think.
If there is a sec=krb5 cifs mount with an *expired* key and you try to access the mount point, the error message is better:
ls: Öffnen von Verzeichnis '.' nicht möglich: Der notwendige Schlüssel ist nicht verfügbar
(in English like "opening directory "." not possible: the required key is not availbale").
A similar message would be good at mount time if the required key is not available.