Print localizedFailureReason for autoUpdater errors

This is to help solve #1292.

atom/browser/auto_updater_mac.mm

@@ -94,7 +94,9 @@ void AutoUpdater::CheckForUpdates() {
           delegate->OnUpdateNotAvailable();
         }
       } error:^(NSError *error) {
-        delegate->OnError(base::SysNSStringToUTF8(error.localizedDescription));
+        delegate->OnError(base::SysNSStringToUTF8(
+            [NSString stringWithFormat:@"%@: %@",
+                error.localizedDescription, error.localizedFailureReason]));
       }];
 }