app, plug-ins: clean up previous commit by using g_error_set()...

... instead of g_message().

(cherry picked from commit 5b9e2776)

app/core/gimpbrush-load.c

@@ -262,7 +262,8 @@ gimp_brush_load_brush (GimpContext  *context,
 
   if (header.header_size < sizeof (BrushHeader))
     {
-      g_message (_("Unsupported brush format"));
+      g_set_error (error, GIMP_DATA_ERROR, GIMP_DATA_ERROR_READ,
+                   _("Unsupported brush format"));
       return NULL;
     }
 

plug-ins/common/file-gbr.c

@@ -415,7 +415,8 @@ load_image (const gchar  *filename,
       bh.header_size += 8;
       if (bh.header_size < sizeof (BrushHeader))
         {
-          g_message (_("Unsupported brush format"));
+          g_set_error (error, G_FILE_ERROR, G_FILE_ERROR_FAILED,
+                       _("Unsupported brush format"));
           g_object_unref (input);
           return -1;
         }