message: POLLING_INTERVAL needn't be pub.
  This is only used within the file watcher and is const, so it
  can't be configured.
diff: @@ -9,7 +9,7 @@ use crc32fast::Hasher;
  use crate::directory::{WatchCallback, WatchCallbackList, WatchHandle};
  -pub const POLLING_INTERVAL: Duration = Duration::from_millis(if cfg!(test) { 1 } else { 500 });
  +const POLLING_INTERVAL: Duration = Duration::from_millis(if cfg!(test) { 1 } else { 500 });
  // Watches a file and executes registered callbacks when the file is modified.
  pub struct FileWatcher {
  