code: def page_not_found(request, template_name='404.html'):
      
      response = render_in_page(request, template_name)
  
      if response:
          return response
  
      template = Template(
          '<h1>Not Found</h1>'
          '<p>The requested URL {{ request_path }} was not found on this server.</p>')
      body = template.render(RequestContext(
          request, {'request_path': request.path}))
      return http.HttpResponseNotFound(body, content_type=CONTENT_TYPE)
docs: Default 404 handler.
  
      Templates: :template:`404.html`
      Context:
          request_path
              The path of the requested URL (e.g., '/app/pages/bad_page/')