title: Relative path to absolute with scrapy
body: <p>I'm trying to crawl a forum for ultimately posts in threads that have links posted in them. Right now I'm just trying to scrape the users names of the posts. But I think there is a problem with the urls not being static.</p>
  
  <pre><code>spider.py
  
  from scrapy.spiders import CrawlSpider
  from scrapy.selector import Selector
  from scrapy.item import Item, Field
  
  
  class TextPostItem(Item):
      title = Field()
      url = Field()
      submitted = Field()
  
  
  class RedditCrawler(CrawlSpider):
      name = 'post-spider'
      allowed_domains = ['flashback.org']
      start_urls = ['https://www.flashback.org/t2637903']
  
  
      def parse(self, response):
          s = Selector(response)
          next_link = s.xpath('//a[@class="smallfont2"]//@href').extract()[0]
          if len(next_link):
              yield self.make_requests_from_url(next_link)
          posts =   Selector(response).xpath('//div[@id="posts"]/div[@class="alignc.p4.post"]')
          for post in posts:
              i = TextPostItem()
              i['title'] = post.xpath('tbody/tr[1]/td/span/text()').extract() [0]
              #i['url'] = post.xpath('div[2]/ul/li[1]/a/@href').extract()[0]
              yield i
  </code></pre>
  
  <p>Provide me the following error:</p>
  
  <pre><code>raise ValueError('Missing scheme in request url: %s' % self._url)
  ValueError: Missing scheme in request url: /t2637903p2
  </code></pre>
  
  <p>Any idea?</p>