Add missing message

git-svn-id: https://svn.apache.org/repos/asf/tomcat/trunk@1485659 13f79535-47bb-0310-9956-ffa450edef68
Better error message

git-svn-id: https://svn.apache.org/repos/asf/tomcat/trunk@1485660 13f79535-47bb-0310-9956-ffa450edef68