[5.2.x] Corrected code examples in topics docs.

Backport of fa804d0d14ef4547b4fe2a88ab5d89d4eed5bacd from main.

docs/topics/class-based-views/generic-editing.txt

@@ -303,7 +303,7 @@ preference, use :func:`django.http.HttpRequest.get_preferred_type`::
 
         def form_invalid(self, form):
             response = super().form_invalid(form)
-            accepted_type = request.get_preferred_type(self.accepted_media_types)
+            accepted_type = self.request.get_preferred_type(self.accepted_media_types)
             if accepted_type == "text/html":
                 return response
             elif accepted_type == "application/json":
@@ -314,7 +314,7 @@ preference, use :func:`django.http.HttpRequest.get_preferred_type`::
             # it might do some processing (in the case of CreateView, it will
             # call form.save() for example).
             response = super().form_valid(form)
-            accepted_type = request.get_preferred_type(self.accepted_media_types)
+            accepted_type = self.request.get_preferred_type(self.accepted_media_types)
             if accepted_type == "text/html":
                 return response
             elif accepted_type == "application/json":

docs/topics/files.txt

@@ -70,7 +70,7 @@ location (:setting:`MEDIA_ROOT` if you are using the default
     >>> from django.conf import settings
     >>> initial_path = car.photo.path
     >>> car.photo.name = "cars/chevy_ii.jpg"
-    >>> new_path = settings.MEDIA_ROOT + car.photo.name
+    >>> new_path = os.path.join(settings.MEDIA_ROOT, car.photo.name)
     >>> # Move the file on the filesystem
     >>> os.rename(initial_path, new_path)
     >>> car.save()

docs/topics/pagination.txt

@@ -31,7 +31,7 @@ accessing the items for each page:
     >>> p.num_pages
     2
     >>> type(p.page_range)
-    <class 'range_iterator'>
+    <class 'range'>
     >>> p.page_range
     range(1, 3)