If you see the message "Attempting deletion of stale pid file." when starting Hyper-Q, it means that a previously running instance of Hyper-Q was not shut down cleanly (e.g., system crash). The PID file of that process is still present. Hyper-Q's startup logic has determined that is does not refer to a live process anymore and has therefore cleaned it up.
No action is required. Hyper-Q has cleaned up the stale PID file and started up.