[gnome-boxes] MachineConfigEditor: Format the error message

[Felipe Borges <felipeborges src gnome org>]

commit 9a9ea6b5f76439dbc13c5a0fd7d6389ffb218a1c
Author: Sebastian Grabowski <sebastian grabel de>
Date:   Mon Mar 1 19:18:39 2021 +0100

    MachineConfigEditor: Format the error message
    
    The error message shown in the notificationbar did not contain the
    actual error message but the %s placeholder when applying an invalid xml
    file. This is fixed here by simply applying the same error message as in
    the debug logs to it.

 src/config-editor.vala | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
---
diff --git a/src/config-editor.vala b/src/config-editor.vala
index a9f1bc75..f40c740e 100644
--- a/src/config-editor.vala
+++ b/src/config-editor.vala
@@ -82,7 +82,7 @@ public async void apply () {
             domain_xml = custom_config.to_xml ();
         } catch (GLib.Error error) {
             warning ("Failed to apply custom VM configuration: %s", error.message);
-            var msg = _("Boxes failed to apply VM configuration changes: %s");
+            var msg = _("Boxes failed to apply VM configuration changes: %s").printf (error.message);
             App.app.main_window.notificationbar.display_error (msg);
 
             return;