How to extract urls from an xml using scrapy - XMLFeedSpider?

I have started using Scrapy recently and I'm trying to use the "XMLFeedSpider" to extract and load the pages that are in a xml page. But the problem is that it is returning an error: "IndexError: list index out of range".

I'm trying to collect and load all product pages that are at this address:
"http://www.example.com/feed.xml"

My spider:

from scrapy.spiders import XMLFeedSpider

class PartySpider(XMLFeedSpider):
    name = 'example'
    allowed_domains = ['http://www.example.com']

    start_urls = [      
        'http://www.example.com/feed.xml'
    ]   

    itertag = 'loc'

    def parse_node(self, response, node): 
        self.logger.info('Hi, this is a <%s> node!: %s', self.itertag,''.join(node.extract()))