protected void onError(Page page, Task task, Throwable e) {
        this.onError(page.getRequest(), task, e);
    }
@param page the {@link Page}.
@param task the {@link Task}.
@param e the exception.
@since 0.10.0
webmagic-core/src/main/java/us/codecraft/webmagic/downloader/AbstractDownloader.java