Handle background fetch errors

Signal/src/AppDelegate.m

@@ -1179,22 +1179,14 @@ static NSTimeInterval launchStartedAt;
 - (void)application:(UIApplication *)application
     performFetchWithCompletionHandler:(void (^)(UIBackgroundFetchResult result))completionHandler
 {
-    OWSLogInfo(@"performing background fetch");
+    NSLog(@"[Loki] Performing background fetch.");
     [AppReadiness runNowOrWhenAppDidBecomeReady:^{
-        // Loki: We don't want to spin up the long poller here as it is probably wasteful on resources
         __block AnyPromise *job = [AppEnvironment.shared.messageFetcherJob run].then(^{
-            // HACK: Call completion handler after n seconds.
-            //
-            // We don't currently have a convenient API to know when message fetching is *done* when
-            // working with the websocket.
-            //
-            // We *could* substantially rewrite the TSSocketManager to take advantage of the `empty` message
-            // But once our REST endpoint is fixed to properly de-enqueue fallback notifications, we can easily
-            // use the rest endpoint here rather than the websocket and circumvent making changes to critical code.
-            dispatch_after(dispatch_time(DISPATCH_TIME_NOW, (int64_t)(5 * NSEC_PER_SEC)), dispatch_get_main_queue(), ^{
-                completionHandler(UIBackgroundFetchResultNewData);
-                job = nil;
-            });
+            completionHandler(UIBackgroundFetchResultNewData);
+            job = nil;
+        }).catch(^{
+            completionHandler(UIBackgroundFetchResultFailed);
+            job = nil;
         });
         [job retainUntilComplete];
     }];