TII-142 better error handling

git-svn-id: https://source.sakaiproject.org/contrib/turnitin/branches/TII-142@84358 fdecad78-55fc-0310-b1b2-d7d25cf747c9
TII-142 imporve error message

git-svn-id: https://source.sakaiproject.org/contrib/turnitin/branches/TII-142@84359 fdecad78-55fc-0310-b1b2-d7d25cf747c9