REDIRECT_FIELD_NAME = 'next'

@sensitive_post_parameters()
@csrf_protect
@never_cache
def login(request, template_name='registration/login.html',
          redirect_field_name=REDIRECT_FIELD_NAME,
          authentication_form=AuthenticationForm,
          current_app=None, extra_context=None):
    """
    Displays the login form and handles the login action.
    """
    redirect_to = request.POST.get(redirect_field_name,
                                   request.GET.get(redirect_field_name, ''))
#
    if request.method == "POST":
        form = authentication_form(request, data=request.POST)
        if form.is_valid():
#
            # Ensure the user-originating redirection url is safe.
            if not is_safe_url(url=redirect_to, host=request.get_host()):
                redirect_to = resolve_url(settings.LOGIN_REDIRECT_URL)
#
            # Okay, security check complete. Log the user in.
            auth_login(request, form.get_user())
#
            return HttpResponseRedirect(redirect_to)
    else:
        form = authentication_form(request)
#
    current_site = get_current_site(request)
#
    context = {
        'form': form,
        redirect_field_name: redirect_to,
        'site': current_site,
        'site_name': current_site.name,
    }
    if extra_context is not None:
        context.update(extra_context)
#
    if current_app is not None:
        request.current_app = current_app
#
    return TemplateResponse(request, template_name, context)

def get_current_site(request):
    """
    Checks if contrib.sites is installed and returns either the current
    ``Site`` object or a ``RequestSite`` object based on the request.
    """
    # Imports are inside the function because its point is to avoid importing
    # the Site models when django.contrib.sites isn't installed.
    if apps.is_installed('django.contrib.sites'):
        from .models import Site
        return Site.objects.get_current(request)
    else:
        from .requests import RequestSite
        return RequestSite(request)

class SiteManager(models.Manager):
     def get_current(self, request=None):
        """
        Returns the current Site based on the SITE_ID in the project's settings.
        If SITE_ID isn't defined, it returns the site with domain matching
        request.get_host(). The ``Site`` object is cached the first time it's
        retrieved from the database.
        """
        from django.conf import settings
        if getattr(settings, 'SITE_ID', ''):
            site_id = settings.SITE_ID
            return self._get_site_by_id(site_id)
        elif request:
            return self._get_site_by_request(request)

        raise ImproperlyConfigured(
            "You're using the Django \"sites framework\" without having "
            "set the SITE_ID setting. Create a site in your database and "
            "set the SITE_ID setting or pass a request to "
            "Site.objects.get_current() to fix this error."
        )

<form method="post" action="">
    {% csrf_token %}
    {{ form.as_p }}
    <input type="submit" value="{% trans 'Log in' %}" />
    <input type="hidden" name="next" value="{{ next }}" />
</form>