Add missing imports and models to the examples in the view layer documentation

docs/ref/template-response.txt

@@ -215,6 +215,7 @@ re-rendered, you can re-evaluate the rendered content, and assign
 the content of the response manually::
 
     # Set up a rendered TemplateResponse
+    >>> from django.template.response import TemplateResponse
     >>> t = TemplateResponse(request, 'original.html', {})
     >>> t.render()
     >>> print(t.content)
@@ -256,6 +257,8 @@ To define a post-render callback, just define a function that takes
 a single argument -- response -- and register that function with
 the template response::
 
+    from django.template.response import TemplateResponse
+
     def my_render_callback(response):
         # Do content-sensitive processing
         do_post_processing()