message: improve the error message here
diff: @@ -631,7 +631,12 @@ where
  // has gone horribly wrong. This panic will
  // (unfortunately) abort the process, but recovery is
  // not possible.
  - _ => panic!("unexpected query state"),
  + _ => panic!(
  + "\
  +Unexpected panic during query evaluation, aborting the process.
  +
  +Please report this bug to https://github.com/salsa-rs/salsa/issues."
  + ),
  }
  } else {
  // If no panic occurred, then panic guard ought to be
  