title: Why is scrapy dumping thousands of `ERROR` log messages without any description of the error?
body: <p>I'm in the process of writing a <code>CrawlSpider</code> that will parse google search results.  The search query changes each time, so the spider must first connect to a database to gather information on the search query it will need to parse.  Here is my anotated <code>CrawlSpider</code> class:</p>
  
  <pre><code>class GoogleSpider(CrawlSpider):
      name = 'googlespider'
      allowed_domains = ['google.com', 'google.ca', 'google.fr']
      logger = log
  
      _google_query = "http://www.google.{0}/search?q={1}"
  
      def __init__(self, *args, **kwargs):
          super(GoogleSpider, self).__init__(*args, **kwargs)
          dispatcher.connect(self.get_startup_params, signals.spider_opened)
  
      @defer.inlineCallbacks
      def get_startup_params(self, spider, **kw):
  
          # Get the exact requests to issue to google
          exreqs = yield get_exactrequests()
  
          # Create the google query (i.e. url to scrape) and store associated information
          start_urls = []
          self.item_lookup = {}
          for keyword, exact_request, lang in exreqs['res']:
              url = self.mk_google_query(lang, exact_request)
              start_urls.append(url)
              self.item_lookup[url] = (keyword, exact_request)
  
          # Assign the google query URLs to `start_urls`
          self.start_urls = tuple(start_urls)
  
      def mk_google_query(self, lang, search_terms):
          return self._google_query.format(lang, quote(search_terms))
  
      def parse_item(self, response):
          sel = Selector(response)
          item = Item()
          keyword, exact_request = self.item_lookup[response.request.url]
          item['urls'] = map(lambda r: r.extract(),
                             sel.xpath('//h3[@class="r"]/a/@href'))
          item['keyword'] = keyword
          item['exactrequest'] = exact_request
          return item
  </code></pre>
  
  <p>When I run <code>scrapy crawl googlespider</code>, I get a <strong>MASSIVE</strong> log output that looks like this:</p>
  
  <blockquote>
    <p>[-] ERROR: 2014-02-17 00:24:38+0100 [-] ERROR: 2014-02-17
    00:24:38+0100 [-] ERROR: 2014-02-17 00:24:38+0100 [-] ERROR:
    2014-02-17 00:24:38+0100 [-] ERROR: 2014-02-17 00:24:38+0100 [-]
    ERROR: 2014-02-17 00:24:38+0100 [-] ERROR: 2014-02-17 00:24:38+0100
    [-] ERROR: 2014-02-17 00:24:38+0100 [-] ERROR: 2014-02-17
    00:24:38+0100 [-] ERROR: 2014-02-17 00:24:38+0100 [-] ERROR:
    2014-02-17 00:24:38+0100 [-] ERROR: 2014-02-17 00:24:38+0100 [-]
    ERROR: 2014-02-17 00:24:38+0100 [-] ERROR: 2014-02-17 00:24:38+0100
    [-] ERROR: 2014-02-17 00:24:38+0100 [-] ERROR: 2014-02-17
    00:24:38+0100 [-] ERROR: 2014-02-17 00:24:38+0100 [-] ERROR:
    2014-02-17 00:24:38+0100 [-] ERROR: 2014-02-17 00:24:38+0100 [-]
    ERROR: 2014-02-17 00:24:38+0100 [-] ERROR: 2014-02-17 00:24:38+0100
    [-] ERROR:     2014-02-17 00:24:38+0100 [-] ERROR: 2014-02-17
    00:24:38+0100 [-] ERROR: 2014-02-17 00:24:38+0100 [-] ERROR:
    2014-02-17 00:24:38+0100 [-] ERROR: 2014-02-17 00:24:38+0100 [-]
    ERROR: 2014-02-17 00:24:38+0100 [-] ERROR: 2014-02-17 00:24:38+0100
    [-] ERROR: 2014-02-17 00:24:38+0100 [-] ERROR: 2014-02-17
    00:24:38+0100 [-] ERROR: 2014-02-17 00:24:38+0100 [-] ERROR:
    2014-02-17 00:24:38+0100 [-] ERROR: 2014-02-17 00:24:38+0100 [-]
    ERROR: 2014-02-17 00:24:38+0100 [-] ERROR: 2014-02-17 00:24:38+0100
    [-] ERROR: 2014-02-17 00:24:38+0100 [-] ERROR: 2014-02-17
    00:24:38+0100 [-] ERROR: 2014-02-17 00:24:38+0100 [-] ERROR:
    2014-02-17 00:24:38+0100 [-] ERROR: 2014-02-17 00:24:38+0100 [-]
    ERROR: 2014-02-17 00:24:38+0100 [-] ERROR: 2014-02-17 00:24:38+0100
    [-] ERROR: 2014-02-17 00:24:38+0100 [-] ERROR: 2014-02-17
    00:24:38+0100 [-] ERROR: 2014-02-17 00:24:38+0100 [-] ERROR:
    2014-02-17 00:24:38+0100 [-] ERROR: 2014-02-17 00:24:38+0100 [-]
    ERROR: 2014-02-17 00:24:38+0100 [-] ERROR: 2014-02-17 00:24:38+0100
    [-] ERROR: 2014-02-17 00:24:38+0100 [-] ERROR: 2014-02-17
    00:24:38+0100 [-] ERROR: 2014-02-17 00:24:38+0100 [-] ERROR:
    2014-02-17 00:24:38+0100 [-] ERROR: 2014-02-17 00:24:38+0100 [-]
    ERROR: 2014-02-17 00:24:38+0100 [-] ERROR: 2014-02-17 00:24:38+0100
    [-] ERROR: 2014-02-17 00:24:38+0100 [-] ERROR: 2014-02-17
    00:24:38+0100 [-] ERROR: 2014-02-17 00:24:38+0100 [-] ERROR:
    2014-02-17 00:24:38+0100 [-] ERROR: 2014-02-17 00:24:38+0100 [-]
    ERROR: 2014-02-17 00:24:38+0100 [-] ERROR: 2014-02-17 00:24:38+0100
    [-] ERROR: 2014-02-17 00:24:38+0100 [-] ERROR: 2014-02-17
    00:24:38+0100 [-] ERROR: 2014-02-17 00:24:38+0100 [-] ERROR:
    2014-02-17 00:24:38+0100</p>
  </blockquote>
  
  <p>This output goes on for (I would estimate) a good 10,000 lines -- far beyond my terminal's scrollback.</p>
  
  <p>Does anybody know what the issue might be and how I should go about diagnosing/fixing it?</p>
  
  <p>Thank you!</p>