code: public static void onHandleError(BiConsumer<Thread, ? super Throwable> c) {
  		if (log.isDebugEnabled()) {
  			log.debug("Hooking new default: onHandleError");
  		}
  		onHandleErrorHook = Objects.requireNonNull(c, "onHandleError");
  	}
docs: Define a hook that is executed when a {@link Scheduler} has
  {@link #handleError(Throwable) handled an error}. Note that it is executed after
  the error has been passed to the thread uncaughtErrorHandler, which is not the
  case when a fatal error occurs (see {@link Exceptions#throwIfJvmFatal(Throwable)}).
  
  @param c the new hook to set.