Improve error display

[SVGAnimate]

Hello,

The message "Printer not found is not displayed.

To get this :

svganimate@work:~$ ./wkgtkprinter -i ... -o ...
WebKitPrintError: Printer not found

Please, add :

1. near line : https://github.com/gnudles/wkgtkprinter/blob/master/wkgtkprinter.c#L14

static void
print_failed (WebKitPrintOperation *print_operation,
               gpointer              error,
               gpointer              user_data)
{
    GError *e = error;
    g_print("%s: %s\n",
             g_quark_to_string(e->domain),
             (gchar*)e->message);
    gtk_main_quit();
}

2. near line : https://github.com/gnudles/wkgtkprinter/blob/master/wkgtkprinter.c#L191

g_signal_connect (print_operation, "failled", G_CALLBACK (print_failed), &user_data);

---

Thanks

[SVGAnimate]

This change can make a difference

    gtk_print_settings_set_printer (print_settings,
                                    "Imprimer dans un fichier");