add_item now returns a Result

src/calendar/remote_calendar.rs

@@ -92,8 +92,8 @@ impl PartialCalendar for RemoteCalendar {
 
 
     /// Add an item into this calendar
-    async fn add_item(&mut self, _item: Item) {
-        log::error!("Not implemented");
+    async fn add_item(&mut self, _item: Item) -> Result<(), Box<dyn Error>> {
+        Err("Not implemented".into())
     }
 
     /// Remove an item from this calendar