message: Panic if current era is before the last upgrade
diff: @@ -144,6 +144,13 @@ where
  registry: &Registry,
  new_consensus: Box<ConsensusConstructor<I>>,
  ) -> Result<(Self, Effects<Event<I>>), Error> {
  + if current_era < protocol_config.last_activation_point {
  + panic!(
  + "Current era ({:?}) is before the last activation point ({:?}) - no eras would \
  + be instantiated!",
  + current_era, protocol_config.last_activation_point
  + );
  + }
  let unit_hashes_folder = config.with_dir(config.value().unit_hashes_folder.clone());
  let (root, config) = config.into_parts();
  let secret_signing_key = Arc::new(config.secret_key_path.clone().load(root)?);
  