OSes tested: Ubuntu 16.04, Centos7
When issuing a trust signature for, say "customer.com", gnupg saves the
trust_regexp to '<[^>]+[@.]customer\.com>$', which looks right. However, when
trust checks are done, that string is passed to sanitize_regexp(), which adds
backslashes before every letter. The resulting regexp doesn't match email
addresses in the domain.
If I modify sanitize_regexp() to leave alphabet letters alone, it matches and
the trust sig works as expected.
I think this is related to bug T2284.
(I have example output and an example patch, but adding these makes the bug
tracker think I'm spam; I'll try to add again later)