src/HOL/Tools/ATP/atp_systems.ML

                      |> `(find_system name versions))
 
 fun the_system name versions =
   case get_system name versions of
     SOME sys => sys
-  | NONE => error ("System " ^ quote name ^ " not available at SystemOnTPTP.")
+  | NONE => error ("System " ^ quote name ^
+                   " is not available at SystemOnTPTP.")
 
 val max_remote_secs = 240 (* give Geoff Sutcliffe's servers a break *)
 
 fun remote_config system_name system_versions proof_delims known_failures
                   default_max_relevant use_conjecture_for_hypotheses