Fixed #21588 -- Corrected handler initialization in "modifying upload handlers" example.

provides feedback on upload progress to some sort of AJAX widget. You'd add this

handler to your upload handlers like this::

    request.upload_handlers.insert(0, ProgressBarUploadHandler())

    request.upload_handlers.insert(0, ProgressBarUploadHandler(request))

You'd probably want to use ``list.insert()`` in this case (instead of

``append()``) because a progress bar handler would need to run *before* any

If you want to replace the upload handlers completely, you can just assign a new

list::

   request.upload_handlers = [ProgressBarUploadHandler()]

   request.upload_handlers = [ProgressBarUploadHandler(request)]

.. note::

        @csrf_exempt

        def upload_file_view(request):

            request.upload_handlers.insert(0, ProgressBarUploadHandler())

            request.upload_handlers.insert(0, ProgressBarUploadHandler(request))

            return _upload_file_view(request)

        @csrf_protect