Hi all,
due the migration to the Kerberos based auth [1] not being finished for secondary koji hubs (arm, ppc, s390), you can see a "ppc.koji.fedoraproject.org uses an invalid security certificate" message and due HTTP Strict Transport Security (HSTS) you are not able to add an exception. This is going to be fixed soon (likely tomorrow). Sorry for the inconvenience.
Dan
[1] https://fedoraproject.org/wiki/ReleaseEngineering/FlagDay2016
secondary@lists.fedoraproject.org