django 1.11 login user

Hi,
 i have try to login user using the guide from https://docs.djangoproject.com/en/1.11/topics/auth/default/

but get an error. Can someone advise what i am doin wrong here

he is my view.py

#Authentication user
def login(request):
    username=request.POST['username']
    password=request.POST['password']
    user=authenticate(request,username=username,password=password)
    if user is not None:
        login(request,user)
        #Redirect to dashboard page
        return render(request,'dashboard.html')
    else:
        # return invalid login message
        return HttpResponse( 'You have enter a wrong password or username please again')

Error message:

Environment:
Request Method: POST
Request URL: http://127.0.0.1:8000/login/

Django Version: 1.11
Python Version: 2.7.12
Installed Applications:
['django.contrib.admin',
 'django.contrib.auth',
 'django.contrib.contenttypes',
 'django.contrib.sessions',
 'django.contrib.messages',
 'django.contrib.staticfiles',
 'fundmanager']
Installed Middleware:
['django.middleware.security.SecurityMiddleware',
 'django.contrib.sessions.middleware.SessionMiddleware',
 'django.middleware.common.CommonMiddleware',
 'django.middleware.csrf.CsrfViewMiddleware',
 'django.contrib.auth.middleware.AuthenticationMiddleware',
 'django.contrib.messages.middleware.MessageMiddleware',
 'django.middleware.clickjacking.XFrameOptionsMiddleware']



Traceback:

File "/root/.virtualenvs/benchmark/local/lib/python2.7/site-packages/django/core/handlers/exception.py" in inner
  41.             response = get_response(request)

File "/root/.virtualenvs/benchmark/local/lib/python2.7/site-packages/django/core/handlers/base.py" in _get_response
  187.                 response = self.process_exception_by_middleware(e, request)

File "/root/.virtualenvs/benchmark/local/lib/python2.7/site-packages/django/core/handlers/base.py" in _get_response
  185.                 response = wrapped_callback(request, *callback_args, **callback_kwargs)

File "/var/www/projects/benchmark/fundmanager/views.py" in login
  22.     username=request.POST['username']

File "/root/.virtualenvs/benchmark/local/lib/python2.7/site-packages/django/utils/datastructures.py" in __getitem__
  85.             raise MultiValueDictKeyError(repr(key))

Exception Type: MultiValueDictKeyError at /login/
Exception Value: "u'username'"

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