message: (Update an error message)
diff: @@ -332,7 +332,7 @@ impl MultiDriver {
  for i in 0..6 {
  let j = *self.layout.get(i) as usize;
  if j >= n {
  - fail!("invalid multi layout index: {} (expected 0-{})", j, n);
  + fail!("invalid multi layout index: {} (expected 0-{})", j, n - 1);
  }
  used[j] = true;
  }
  