message: Fail on unhandled `FinalitySignature` message variant in joiner reactor.
diff: @@ -557,6 +557,9 @@ impl reactor::Reactor for Reactor {
  });
  self.dispatch_event(effect_builder, rng, event)
  }
  + Message::FinalitySignature(_) => {
  + unimplemented!("Finality signatures not handled in joiner reactor")
  + }
  other => {
  warn!(?other, "network announcement ignored.");
  Effects::new()
  