small change to error message for plugins to let people know about Check plugin being mandatory
small change to error message for plugins to let people know about Check plugin being mandatory

git-svn-id: e9fe9b84e32fc5e57b7d09c40cd78b14ea28ed71@1651169 13f79535-47bb-0310-9956-ffa450edef68

apache/spamassassin,apache/spamassassin,apache/spamassassin,apache/spamassassin,apache/spamassassin