message: Address both Clippy's and Fraser's complaints
diff: @@ -4,6 +4,7 @@ use std::{
  env, fmt,
  fmt::{Debug, Display, Formatter},
  str::FromStr,
  + thread,
  time::Duration,
  };
  @@ -141,7 +142,7 @@ where
  match env::var(name) {
  Ok(raw) => Some(
  raw.parse()
  - .expect(&format!("cannot parse envvar `{}`", name)),
  + .unwrap_or_else(|_| panic!("cannot parse envvar `{}`", name)),
  ),
  Err(env::VarError::NotPresent) => None,
  Err(err) => {
  @@ -187,7 +188,7 @@ async fn send_large_message_across_network() {
  // Hack to get network component to connect. This gives the libp2p thread (which is independent
  // of cranking) a little time to bind to the socket.
  - std::thread::sleep(std::time::Duration::from_secs(2));
  + thread::sleep(Duration::from_secs(2));
  // Create `node_count-1` additional node instances.
  for _ in 1..node_count {
  