message: ensure the inotify fd is valid
  this could happen for example if the user hits a limit on the number of file
  descriptor
diff: @@ -23,7 +23,9 @@ WatcherImpl::WatcherImpl(Event::Dispatcher& dispatcher)
  onInotifyEvent();
  },
  Event::FileTriggerType::Edge,
  - Event::FileReadyType::Read)) {}
  + Event::FileReadyType::Read)) {
  + RELEASE_ASSERT(inotify_fd_ >= 0);
  +}
  WatcherImpl::~WatcherImpl() { close(inotify_fd_); }
  