tuned;

--- a/src/Pure/Tools/build.ML	Sun Mar 29 12:11:02 2020 +0200
+++ b/src/Pure/Tools/build.ML	Sun Mar 29 12:30:27 2020 +0200
@@ -219,6 +219,10 @@
       if name = Context.PureN then Theory.install_pure (Thy_Info.get_theory Context.PureN) else ();
   in () end;
 
+fun inline_errors exn =
+  Runtime.exn_message_list exn
+  |> List.app (fn msg => writeln ("\ferror_message = " ^ encode_lines (YXML.content_of msg)));
+
 (*command-line tool*)
 fun build args_file =
   let
@@ -226,11 +230,10 @@
     val _ = Options.load_default ();
     val _ = Isabelle_Process.init_options ();
     val args = decode_args (File.read (Path.explode args_file));
-    fun error_message msg = writeln ("\ferror_message = " ^ encode_lines (YXML.content_of msg));
     val _ =
       Unsynchronized.setmp Private_Output.protocol_message_fn protocol_message
         build_session args
-      handle exn => (List.app error_message (Runtime.exn_message_list exn); Exn.reraise exn);
+      handle exn => (inline_errors exn; Exn.reraise exn);
     val _ = Private_Output.protocol_message_fn := Output.protocol_message_undefined;
     val _ = Options.reset_default ();
   in () end;