message: Explain why sorting is needed
diff: @@ -18,7 +18,9 @@ impl<E: Ord + AsRef<str>> LimitedDisplay for BTreeSet<E> {
  impl<E: Ord + AsRef<str>> LimitedDisplay for HashSet<E> {
  fn to_string_limited(&self, max_length: usize) -> String {
  - let sorted = BTreeSet::from_iter(self); // TODO: do we want to sort this?
  + // Iteration order in HashSet is undeterminstic. We sort
  + // here to be on the safe side and to simplify testing.
  + let sorted = BTreeSet::from_iter(self);
  sorted.to_string_limited(max_length)
  }
  }
  