RxJavaのmapでのエラー処理(onError)

MainActivity.java

    private void checkRxJavaOnError() {
        String[] urls = {"https://www.google.co.jp/?gws_rd=ssl",
                "http://techium.hatenablog.com/",
                "http://localhost/"};

        Observable
                .from(urls)
                .subscribeOn(Schedulers.newThread())
                .map(new Func1<String, Boolean>() {

                    @Override
                    public Boolean call(String s) {
                        Log.d("techium", s);
                        String result = null;
                        Request request = new Request.Builder()
                                .url(s)
                                .get()
                                .build();

                        OkHttpClient client = new OkHttpClient.Builder()
                                .connectTimeout(10, TimeUnit.SECONDS)
                                .writeTimeout(10, TimeUnit.SECONDS)
                                .readTimeout(10, TimeUnit.SECONDS)
                                .build();
                        try {
                            Response response = client.newCall(request).execute();
                            result = response.body().string();
                        } catch (IOException e) {
                            throw Exceptions.propagate(e);
                        }

                        return true;
                    }
                }).subscribe(new Observer<Boolean>() {

            @Override
            public void onCompleted() {
                Log.d("techium", "onCompleted");
            }

            @Override
            public void onError(Throwable e) {
                Log.d("techium", "onError");
                e.printStackTrace();
            }

            @Override
            public void onNext(Boolean b) {
                Log.d("techium", "onNext " + b);
            }
        });
    }