title: vscode debug python scrapy not step into callback function
body: <p>testing crawler:</p>
  
  <pre><code>class QuotesSpider(scrapy.Spider):
  name = "quotes"
  
  def start_requests(self):
      urls = [
          'http://quotes.toscrape.com/page/1/',
          'http://quotes.toscrape.com/page/2/',
      ]
      for url in urls:
          yield scrapy.Request(url=url, callback=self.parse)
  
  def parse(self, response):
      page = response.url.split("/")[-2]
      filename = 'quotes-%s.html' % page
      with open(filename, 'wb') as f:
          f.write(response.body)
      self.log('Saved file %s' % filename)
  </code></pre>
  
  <p>and I wrote an main.py:</p>
  
  <pre><code>sys.path.append(os.path.dirname(os.path.abspath(__file__)))
  execute(["scrapy","crawl","quotes"])
  </code></pre>
  
  <p>and I added python scrapy debugger config, all are fine, until hit
  yield scrapy.Request(url=url, callback=self.parse)
  it doesn't step into the callback parse function?</p>