Hi!
I was checking CUPS TLS connectivity with gnutls-cli command like:

gnutls-cli -d 1 localhost -p 631

with cups-2.2.10, but it ends with error:

• Status: The certificate is NOT trusted. The certificate issuer is unknown. The name in the certificate does not match the expected.
  *** PKI verification of server certificate failed...
  *** Fatal error: Error in the certificate.

I have full gnutls log
gnutls_debug_output.txt and cups logs
cups_log.txt . I tried it with cups-2.2.7 in Ubuntu, with same results.
I found three commits which could be connected to the issue - ff82ce1 af62b31 e625fa1 , but none of them fixed the issue.
Is it expected behavior or my misconfiguration? Or it is a bug? When I try it in RHEL 7 with cups-1.6.3, it worked correctly.