Grammar fix in error message

hugolib/site.go

@@ -788,7 +788,7 @@ func (s *Site) assembleMenus() {
 
 		for name, me := range p.Menus() {
 			if _, ok := flat[twoD{name, me.KeyName()}]; ok {
-				jww.ERROR.Printf("Two or more menu items have the same name/identifier in %q Menu. Identified as %q.\n Rename or set a unique identifier. \n", name, me.KeyName())
+				jww.ERROR.Printf("Two or more menu items have the same name/identifier in Menu %q: %q.\nRename or set an unique identifier.\n", name, me.KeyName())
 				continue
 			}
 			flat[twoD{name, me.KeyName()}] = me