message: [network] eliminate unreachable that is very reachable
  Closes:
diff: @@ -318,19 +318,11 @@ where
  oneshot::Sender<Result<(), PeerManagerError>>,
  )>,
  ) -> Result<(), PeerManagerError> {
  - trace!("Received message from Peer {}", self.peer_id().short_str(),);
  + trace!("Received message from Peer {}", self.peer_id().short_str());
  // Read inbound message from stream.
  let message = message.freeze();
  let message: NetworkMessage = lcs::from_bytes(&message)?;
  match message {
  - NetworkMessage::RpcRequest(_) | NetworkMessage::RpcResponse(_) => {
  - let notif = PeerNotification::NewMessage(message);
  - self.rpc_notifs_tx.send(notif).await.map_err(|err| {
  - warn!("Failed to send notification to RPC actor. Error: {:?}", err);
  - err
  - })?;
  - Ok(())
  - }
  NetworkMessage::DirectSendMsg(_) => {
  let notif = PeerNotification::NewMessage(message);
  self.direct_send_notifs_tx
  @@ -343,17 +335,32 @@ where
  );
  err
  })?;
  - Ok(())
  + }
  + NetworkMessage::Error(error) => {
  + warn!(
  + "Peer {} sent an error message: {:?}",
  + self.peer_id().short_str(),
  + error,
  + );
  }
  NetworkMessage::Ping(nonce) => {
  let pong = NetworkMessage::Pong(nonce);
  let (ack_tx, _) = oneshot::channel();
  // Resond to a ping right away.
  write_reqs_tx.send((pong, ack_tx)).await?;
  - Ok(())
  }
  - _ => unreachable!("Unhandled"),
  + NetworkMessage::Pong(_nonce) => {
  + // TODO(davidiw) forward to a pong pub/sub and move HealthChecker to leverage this
  }
  + NetworkMessage::RpcRequest(_) | NetworkMessage::RpcResponse(_) => {
  + let notif = PeerNotification::NewMessage(message);
  + self.rpc_notifs_tx.send(notif).await.map_err(|err| {
  + warn!("Failed to send notification to RPC actor. Error: {:?}", err);
  + err
  + })?;
  + }
  + };
  + Ok(())
  }
  async fn handle_request<'a>(
  