src/Pure/System/isabelle_process.ML

     Output.warning_fn := (fn s => standard_message (serial_props ()) Markup.warningN s);
     Output.error_message_fn :=
       (fn (i, s) => standard_message (Markup.serial_properties i) Markup.errorN s);
     Output.system_message_fn := message Markup.systemN [];
     Output.protocol_message_fn := message Markup.protocolN;
-    Output.urgent_message_fn := ! Output.writeln_fn;
     Output.prompt_fn := ignore;
     message Markup.initN [] [Session.welcome ()];
     msg_channel
   end;