improve error message handling

src/grew_args.ml

@@ -117,7 +117,7 @@ module Grew_args = struct
   | "-debug_loop" :: args -> Rewrite.set_debug_loop (); loop args
   | "-dep_dir" :: dir :: args -> dep_dir := Some dir; loop args
 
-  | x -> Log.fwarning "Ignored arguments: %s" (String.concat " " x)
+  | x :: args -> Log.fwarning "Invalid argument: %s, it is ignored!" x; loop args
 
   let parse () =
     match Array.to_list Sys.argv with

src/grew_corpus.ml

@@ -19,9 +19,7 @@ open Grew_args
 
 (* -------------------------------------------------------------------------------- *)
 
-let fail msg =
-  let rule = String.make (String.length msg) '=' in
-  Log.fwarning "\n%s\n%s\n%s" rule msg rule; exit 2
+let fail msg = Log.fmessage "%s" msg; exit 2
 
 let handle fct () =
   try fct ()

src/grew_main.ml

@@ -31,8 +31,7 @@ let _ =
   | Grew_args.Gui args ->
     let gui_exec = if Sys.argv.(0) = "grew_dev" then "grew_gui_dev" else "grew_gui" in
     match Unix.system (gui_exec ^ " " ^ args) with
-    | Unix.WEXITED i when i <> 0 ->
-      Log.warning "It seems that grew_gui is not installed on your system. Try to run \"opam install grew_gui\""
+    | Unix.WEXITED 127 -> Log.message "It seems that grew_gui is not installed on your system. See [http://grew.fr/gtk] for more information"
     | _ -> ()