message: some more logging
diff: @@ -183,6 +183,7 @@ where
  /// corresponding future
  fn poll_aggregation(&mut self, cx: &mut Context) -> Poll<()> {
  if let Some(ref mut fut) = self.aggregation_future {
  + trace!("polling aggregation future");
  match ready!(Pin::new(fut).poll(cx)) {
  // FIXME: there are lots of things to think about
  // when aggregation has failed. Currently the
  @@ -190,8 +191,14 @@ where
  // number. But we also need to make sure that the
  // aggregators is reset and that the global weights
  // are not updated.
  - Ok(()) => self.protocol.end_aggregation(true),
  - Err(()) => self.protocol.end_aggregation(false),
  + Ok(()) => {
  + info!("aggregation finished successfully");
  + self.protocol.end_aggregation(true);
  + }
  + Err(()) => {
  + info!("aggregation failed");
  + self.protocol.end_aggregation(false);
  + }
  }
  self.aggregation_future = None;
  self.handle_protocol_events();
  