These lines:
https://github.com/aerogear/aerogear-unifiedpush-server/blob/master/push/src/main/java/org/jboss/aerogear/unifiedpush/message/sender/APNsPushNotificationSender.java#L116-L117

are invoked in a few cases:

• no certificate in the database (e.g. some smart DBA deleted it there)
• certificate revoked at the Apple Developer Network site

Wondering, if we should replace "No certificate was found" with something like "No (valid) certificate was found. Did you revoke it at the Apple Developer Center" ?