def load(self, spider_name):
        """
        Return the Spider class for the given spider name. If the spider
        name is not found, raise a KeyError.
        """
        try:
            return self._spiders[spider_name]
        except KeyError:
            raise KeyError("Spider not found: {}".format(spider_name))

        Return the Spider class for the given spider name. If the spider
        name is not found, raise a KeyError.
        
stackoverflow/venv/lib/python3.6/site-packages/scrapy/spiderloader.py