ValueError异常：（Django1.11.1 python3.6.1 pycharm）

当我试图用在index.html的设置用户名和密码登录，出现错误如下：ValueError异常：（Django1.11.1 python3.6.1 pycharm）

ValueError at /login_action/ 
The view sign.views.login_action didn't return an HttpResponse object. It      returned None instead. 
Request Method: POST 
Request URL: http://127.0.0.1:8000/login_action/ 
Django Version: 1.11.1 
Exception Type: ValueError 
Exception Value:  
The view sign.views.login_action didn't return an HttpResponse object. It returned None instead. 
Exception Location: D:\python3.6.1\lib\site-  packages\django\core\handlers\base.py in _get_response, line 198 
Python Executable: D:\python3.6.1\python.exe 
Python Version: 3.6.1 
Python Path:  
['C:\\Users\\Administrator\\guest', 
'D:\\python3.6.1\\python36.zip', 
'D:\\python3.6.1\\DLLs', 
'D:\\python3.6.1\\lib', 
'D:\\python3.6.1', 
'D:\\python3.6.1\\lib\\site-packages'] 
Server time: Mon, 12 Jun 2017 08:29:35 +0000

从暗示吗说，HttpResponse对象的valut是无

urls.py作为遵循

from django.conf.urls import url 
from django.contrib import admin 
from sign import views 
urlpatterns = [ 
url(r'^admin/', admin.site.urls), 
url(r'^index/$',views.index), 
url(r'^login_action/$',views.login_action), 
]

views.py作为遵循

from django.shortcuts import render 
from django.http import HttpResponse 
# Create your views here. 
def index(request): 
return render(request,"index.html") 
# 登录函数定义 
def login_action(request): 
if request.method == 'post': 
    username = request.POST.get('username','') 
    password = request.POST.get('password','') 
    if username == 'admin'and password == 'admin123': 
     return HttpResponse('恭喜您，登录成功!') 
    else: 
     return render(request,'index.html',{'error':'用户名或者登录密码错误!'})

index.html作为跟随

<html> 
<head> 
    <title>欢迎登陆点米年会发布会系统</title> 
</head> 
<body> 
<h1>年会签名系统登陆<br> 
    WELCOM TO DIAN MI</h1> 
<form method="post" action="/login_action/"> 
<input name="username" type="text" placeholder="用户名"><br> 
<input name="password" type="password" placeholder="登录密码"><br> 
    <button id="btn" type="submit"> 登陆</button> 
{{error}}<br> 
</form> 
</body> 
</html>

the screenshot of the traceback of the error

来源

2017-06-12 Wendy.Wang