title: Django2.0，python-version3.6，django-simpl-captcha-5.6，Why is my verification code not appearing?
body: <p>I tried to practice a html page for user login.I browse the document and follow the steps to try django-simple-captcha to verify my user login.finally...
  <a href="https://i.stack.imgur.com/fSODt.png" rel="nofollow noreferrer">enter image description here</a></p>
  
  <p>I have already makemigrations, migrate and add captcha to the INSTALL_APPS，and Defined the Form , and Defined view function</p>
  
  <pre><code>'views.py'
  from django.shortcuts import render
  from django.views.generic.base import View
  
  from .froms import UserLoginForm
  # Create your views here.
  class LoginView(View):
      def get(self, request):
      user_login_form = UserLoginForm()
      return render(request, 'login.html', {'user_login_form':user_login_form})
  
  
  'forms.py'
   from django import forms
   from captcha.fields import CaptchaField
  
  class UserLoginForm(forms.Form):
      username = forms.CharField(required=True)
      password = forms.CharField(required=True, min_length=5)
      captcha = CaptchaField()
  
  'urls.py'
  from django.contrib import admin
  from django.urls import path, include
  from django.views.generic import TemplateView
  
  urlpatterns = [
      path('admin/', admin.site.urls),
      path('login/', TemplateView.as_view(template_name='login.html')),
      path('captcha/', include('captcha.urls')),
  ]
  </code></pre>
  
  <p><div class="snippet" data-lang="js" data-hide="false" data-console="true" data-babel="false">
  <div class="snippet-code">
  <pre class="snippet-code-html lang-html prettyprint-override"><code>&lt;html&gt;
   &lt;head&gt;
    &lt;title&gt;login&lt;/title&gt;
   &lt;/head&gt;
   &lt;body&gt;
    &lt;form action="#" method="post"&gt;
     &lt;p&gt;
      Username:&lt;input type="text" name="username" placeholder="Please input you email"&gt;
     &lt;/p&gt;
     &lt;p&gt;
      Password:&lt;input type="password" name="password"&gt;
     &lt;/p&gt;
     &lt;p&gt;
      &lt;label&gt;code:&lt;/label&gt;
         {{ user_login_form.captcha }}
              &lt;/p&gt;
     &lt;input type="submit" value="submit"&gt;
    &lt;/form&gt;
   &lt;/body&gt;
  &lt;/html&gt;</code></pre>
  </div>
  </div>
  </p>