title: scrapy: request url must be str or unicode got list
body: <p>I cant quite figure out what's wrong with this code. I would like to scrape the first page, and then, for each link on that page, go to the second page to extract the item description. When i run the code below, i get: <strong>exception.TypeError: url must be str or unicode, got list</strong>. here is my code:</p>
  
  <pre><code>from scrapy.spider import Spider
  from scrapy.selector import Selector
  from scrapy.http import Request
  from scrapy.item import Item, Field
  from scrapy.contrib.loader import ItemLoader
  from scrapy.contrib.loader.processor import MapCompose,  Join
  from scrapy.contrib.loader import XPathItemLoader
  from my.items import myItem
  
  class mySpider(Spider):
      name = "my"
      allowed_domains = ["my.com"]
      start_urls = ['http://sjg.my.com/cf_jy.cfm']
  
      def parse(self, response):
          s = Selector(response)
          rows = s.xpath('//table[@class="table-order"]//tr')
          for row in rows:
              l = XPathItemLoader(item=myItem(), selector=row)
              l.default_input_processor = MapCompose(unicode.strip)
              l.default_output_processor = Join()
              l.add_xpath('title', './/a[contains(@href,"cf_jy.cfm?hu_pg")]/text()')
              l.add_xpath('url1', './/a/@href')
              l.add_xpath('dates', './/td[4]/text()')
              l.add_xpath('rev', './/td[@align="right"]/text()')
              l.add_xpath('typ', './/td[3]/text()')
              l.add_value('name', u'gsf')
              request = Request(l.get_xpath('.//a/@href'), callback=self.parse_link,meta={'l':l})
              yield request      
  
      def parse_link(self, response):
          l = response.meta["l"]
          s = Selector(response)
          q = s.xpath("//div[@class='content-main']/td[@class='text']/p/text()").extract()
          l.add_value('description',q)
          yield l.load_item()
  </code></pre>
  
  <p>Thanks in advance.</p>