message: use is_power_of_two where appropriate
diff: @@ -68,7 +68,7 @@ fn page_size() {
  // In particular, this checks that it is not 0.
  assert!(
  - page_size.next_power_of_two() == page_size,
  + page_size.is_power_of_two(),
  "page size not a power of two: {}",
  page_size
  );
  