例如
http://v2ex.appspot.com/rework 正常。http://v2ex.appspot.com/rework/ 出错。
Traceback (most recent call last):
File "/base/python_runtime/python_lib/versions/1/google/appengine/ext/webapp/__init__.py", line 511, in __call__
handler.get(*groups)
File "/base/data/home/apps/v2ex/1.346454912655223174/main.py", line 855, in get
if page.mode == 1:
AttributeError: 'NoneType' object has no attribute 'mode'