出现异常：io.reactivex.exceptions.UndeliverableException
出现原因：调用了多次onError，正常来说，出现一次onError会走正常Observer处理，其他的会走Error handling ,可以通过以下捕捉多次的error：

RxJavaPlugins.setErrorHandler(new Consumer<Throwable>() {
            @Override
            public void accept(Throwable e) {
                if (e instanceof UndeliverableException) {
                    e = e.getCause();
                }
                if ((e instanceof IOException)) {
                    // fine, irrelevant network problem or API that throws on cancellation
                    return;
                }
                if (e instanceof InterruptedException) {
                    // fine, some blocking code was interrupted by a dispose call
                    return;
                }
                if ((e instanceof NullPointerException) || (e instanceof IllegalArgumentException)) {
                    // that's likely a bug in the application
                    Thread.currentThread().getUncaughtExceptionHandler().uncaughtException(Thread.currentThread(), e);
                    return;
                }
                if (e instanceof IllegalStateException) {
                    // that's a bug in RxJava or in a custom operator
                    Thread.currentThread().getUncaughtExceptionHandler().uncaughtException(Thread.currentThread(), e);
                    return;
                }
                Logger.l("Undeliverable exception");
            }
        });