title: xlsxwriter can not create file when using scrapy callback in recursive
body: <p>xlsxwriter can not create file in recursive, anyone can take a look?</p>
  
  <pre><code>import scrapy
  import xlsxwriter
  
  class QuotesSpider(scrapy.Spider):
      name = "quotes"
      def start_requests(self):
          start_urls = [
              'https://www.hotelgg.com/venue/mittitlt/', 
          ]
  </code></pre>
  
  <p>create workbook</p>
  
  <pre><code>        filename = 'hotel-list.xlsx'
          wb = xlsxwriter.Workbook(filename)
          self.wb = wb
          if start_urls[0] == 'https://www.hotelgg.com/venue/mittitlt/':
              self.ws = wb.add_worksheet("nanshan")
  </code></pre>
  
  <p>sent request to crawl</p>
  
  <pre><code>        yield scrapy.Request(url=start_urls[0], callback=self.parse)
  
      def parse(self, response):
          ws = self.ws
          i = 0
          # parse response
          for quote in response.css('ul.hotel_list div.info'):
              item = {
                  'name': quote.css('h3.title a::text').extract_first(),
                  'region': quote.css('span.region::text').extract_first(),
                  'street': quote.css('span.street::text').extract_first(),
                  'space': quote.css('span.meetingroom_space_range::text').extract(),
              }
  </code></pre>
  
  <p>write row into excel</p>
  
  <pre><code>            ws.write_string(i, 0, item['name'])
              ws.write_string(i, 1, item['region'])
              ws.write_string(i, 2, item['street'])
              if item['space']:
                  ws.write_string(i, 3, item['space'][1])
              else:
                  ws.write_string(i, 3, '0')
              i += 1
  </code></pre>
  
  <p>get next page for crawling</p>
  
  <pre><code>        next_page = response.css('div.pager a:last-child::attr(href)').extract_first()
          self.log(next_page)
          if next_page is not None:
              next_page = response.urljoin(next_page)
  </code></pre>
  
  <p>sent request for next page</p>
  
  <pre><code>            yield scrapy.Request(next_page, callback=self.parse)
  </code></pre>