code: public final Flux<T> doOnError(Predicate<? super Throwable> predicate,
  			final Consumer<? super Throwable> onError) {
  		Objects.requireNonNull(predicate, "predicate");
  		return doOnError(t -> {
  			if (predicate.test(t)) {
  				onError.accept(t);
  			}
  		});
  	}
docs: Add behavior (side-effect) triggered when the {@link Flux} completes with an error matching the given exception.
  <p>
  <img class="marble" src="doc-files/marbles/doOnErrorWithPredicateForFlux.svg" alt="">
  
  @param predicate the matcher for exceptions to handle
  @param onError the error handler for each error
  
  @return an observed  {@link Flux}