[1.4.x] Fixed #20730 -- Fixed "Programmatically creating permissions" error.

Thanks glarrain for the report.

Backport of 684a606a4e from master

docs/topics/auth.txt

@@ -1654,10 +1654,11 @@ While custom permissions can be defined within a model's ``Meta`` class, you
 can also create permissions directly. For example, you can create the
 ``can_publish`` permission for a ``BlogPost`` model in ``myapp``::
 
+    from myapp.models import BlogPost
     from django.contrib.auth.models import Group, Permission
     from django.contrib.contenttypes.models import ContentType
 
-    content_type = ContentType.objects.get(app_label='myapp', model='BlogPost')
+    content_type = ContentType.objects.get_for_model(BlogPost)
     permission = Permission.objects.create(codename='can_publish',
                                            name='Can Publish Posts',
                                            content_type=content_type)