[pkg-gnupg-maint] Bug#895646: gnupg: do not allow short key IDS in gpg.conf

[Taowa]

Would this be acceptable behaviour:

- If the short key ID matches only one key in the keyring (and that key is ultimately trusted, maybe), issue a warning to the user (the assumption being that the user almost definitely has their own key in their keyring)

- If the short key ID matches multiple key IDs, fail with an error and tell the user to change their gpg.conf

Taowa