message: reactor.network.UTPServer: Propagate send_to errors to utp backend.
diff: @@ -85,7 +85,11 @@ namespace reactor
  copy[i] ^= server->xorify();
  buf = elle::WeakBuffer(copy.contents(), copy.size());
  }
  - server->send_to(buf, ep);
  + server->send_to(buf, ep, [ctx=args->context, ep, header = elle::Buffer(args->buf, std::min(args->len, (size_t)20))]
  + (boost::system::error_code const& e) {
  + ELLE_TRACE("UTP send error on %s: %s", ep, e.message());
  + utp_process_icmp_error(ctx, header.contents(), header.size(), ep.data(), ep.size());
  + });
  return 0;
  }
  