Python 3.x 爬行蜘蛛不'；t调用self.parse（）

我有一个爬行蜘蛛脚本，它使用splash登录javascript页面。但是，在成功登录之后，继承的self.parse（）函数似乎没有被调用。爬行第一页后，爬行器关闭

我认为爬行蜘蛛会在start_请求产生响应后自动调用self.parse方法。但即使使用显式回调，self.parse似乎也不会被调用

我做错了什么

剧本：

#!/usr/bin/env python3
from scrapy.linkextractors import LinkExtractor
from scrapy.spiders import CrawlSpider, Rule
from harvest.items import HarvestItem
from scrapy_splash import SplashRequest


class TestSpider(CrawlSpider):
    name = 'test'
    allowed_domains = ['test.secure.force.com', 'login.salesforce.com']
    login_url = 'https://test.secure.force.com/jSites_Home'

    rules = (Rule(LinkExtractor(restrict_xpaths='//*[@id="nav"]/ul/li/a[@title="Assignments"]')),
             Rule(LinkExtractor(restrict_xpaths='//*/table/tbody/tr[2]/td[1]/a'), callback='parse_item'),
             )

    def start_requests(self):
        script = """
        function main(splash)
            local url = splash.args.url
            assert(splash:go(url))
            assert(splash:wait(10))

            splash:set_viewport_full()

            local search_input = splash:select('input[name=username]')   
            search_input:send_text("someuser")
            local search_input = splash:select('input[name=pw]')
            search_input:send_text("p4ssw0rd")
            assert(splash:wait(5))
            local submit_button = splash:select('input[class=btn]')
            submit_button:click()

            assert(splash:wait(10))

            return {html = splash:html(),}
          end
        """
        headers = {'User-Agent': 'Mozilla/5.0 (Macintosh; Intel Mac OS X 10_12_2) AppleWebKit/537.36 (KHTML, like Gecko'
                                 ') Chrome/55.0.2883.95 Safari/537.36'}
        yield SplashRequest(url=self.login_url,
                            callback=self.parse,
                            endpoint='execute',
                            args={
                                'lua_source': script,
                                'wait': 5
                                },
                            splash_headers=headers,
                            headers=headers)

    def parse_item(self, response):
        items = HarvestItem()
        items['start'] = response.xpath('(//*/table[@class="detailList"])[3]/tbody/tr[1]/td[1]/span/text()').extract()
        return items