scrapy 爬虫错误求助

错误：
ImportError: No module named items

程序：

items.py代码：
# Define here the models for your scraped items
#
# See documentation in:
# http://doc.scrapy.org/en/latest/topics/items.html

from scrapy.item import Item, Field

class XsItem(Item):
# define the fields for your item here like:
# name = Field()
url = Field()

xs.py代码：
from scrapy.contrib.spiders import CrawlSpider, Rule
from scrapy.contrib.linkextractors.sgml import SgmlLinkExtractor
from scrapy.selector import Selector

from xs.items import XsItem

class XsSpider(CrawlSpider):
name = 'xs'
allowed_domains = ['bbs.uc.cn']
start_urls = ['http://bbs.uc.cn']

rules = (
Rule(SgmlLinkExtractor(allow=('\thread-\d+-\d-\d.html', )),
callback='parse_page', follow=True),
)

def parse_page(self, response):
item = XsItem()
sel = Selector(response)
item['url'] = response.url
return item