let sequenceWithError = Observable<Int>.create {
    $0.on(.next(1))
    $0.on(.next(2))
    $0.on(.next(3))
    $0.on(.next(4))
    $0.onError(RxError.unknown)
    $0.on(.next(5))
    return Disposables.create {

    }
}
let sequenceIgnoreError = sequenceWithError.catchError{_ in
    return Observable.of(10,11,12)
}
_ = sequenceIgnoreError.subscribe{
    print($0)
}