[gimp] app: print gimp_versions.json parsing error on stderr.

[Jehan <jehanp src gnome org>]

commit 7f3bb72c8ce0f7cdc39c2a6476b5b05eea725342
Author: Jehan <jehan girinstud io>
Date:   Mon Mar 30 14:40:20 2020 +0200

    app: print gimp_versions.json parsing error on stderr.
    
    Do it even on stable builds as it can help diagnose bugs on releases.
    Note that the issue we had just know with casing on the build-id would
    not have been seen by such stderr output anyway. Just in case for future
    issues.
    
    (cherry picked from commit dd4cec577dd146720ccebd99e33618177773d5d2)

 app/gimp-update.c | 4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)
---
diff --git a/app/gimp-update.c b/app/gimp-update.c
index 4ee1ce6127..f64a5442fa 100644
--- a/app/gimp-update.c
+++ b/app/gimp-update.c
@@ -115,10 +115,8 @@ gimp_check_updates_callback (GObject      *source,
       parser = json_parser_new ();
       if (! json_parser_load_from_stream (parser, G_INPUT_STREAM (stream), NULL, &error))
         {
-#ifdef GIMP_UNSTABLE
-          g_printerr("Parsing of %s failed: %s\n",
+          g_printerr("%s: parsing of %s failed: %s\n", G_STRFUNC,
                      g_file_get_uri (G_FILE (source)), error->message);
-#endif
           g_clear_object (&stream);
           g_clear_object (&parser);
           g_clear_error (&error);