求助，爬虫运行失败，错误提示如下
C:\Python27\python.exe C:/Users/Administrator/PycharmProjects/baike/baike/spider_main.py
craw 1 : https://baike.baidu.com/item/Python/407313?fr=aladdin
Traceback (most recent call last):
File "C:/Users/Administrator/PycharmProjects/baike/baike/spider_main.py", line 34, in <module>
obj_spider.craw(root_url)
File "C:/Users/Administrator/PycharmProjects/baike/baike/spider_main.py", line 19, in craw
new_urls,new_data = self.parser.parse(new_url,html_cont)
TypeError: 'NoneType' object is not iterable
Process finished with exit code 1
