在 Django 网站上找不到页面 404

我将按照Django网站上的教程创建一个简单的投票应用程序.但是，Django无法解析"//127.0.0.1:8000/Polls"，即使我已经在MySite/urls.py中定义了正则表达式.我在一个安装了最新Django(1.7)的虚拟环境中执行此操作.

MySite/urls.py:

from django.conf.urls import patterns, include, url
from django.contrib import admin

urlpatterns = patterns('',
url(r'^admin/', include(admin.site.urls)),
url(r'^polls/', include('polls.urls')),
)

MySite/Polls/urls.py:

from django.conf.urls import patterns, url
from polls import views

urlpatterns = patterns('',
url(r'^$', views.index, name='index'), 
)

MySite/Polls/views.py:

from django.shortcuts import render
from django.http import HttpResponse
def index(request):
    return HttpResponse("Hello, world. You're at the polls index.")

mySite/settings.py:

 ...
 INSTALLED_APPS = (
'django.contrib.admin',
'django.contrib.auth',
'django.contrib.contenttypes',
'django.contrib.sessions',
'django.contrib.messages',
'django.contrib.staticfiles',
'polls',
 ) 
  ....
 ROOT_URLCONF = 'mySite.urls'

我收到的错误是:

Using the URLconf defined in mySite.urls, Django tried these URL patterns, in this order: ^admin/  
The current URL, polls, didn't match any of these.