"MarkupField" for displaying raw markup in a Django form

Sometimes you need to break up a form into sections with subtitles, or <div>s, or whatever, but Django's form API does not (that I was able to tell) provide a way to do this out of the box, so I implemented a custom field type and widget that just displays whatever raw markup is passed to it. (Use with caution, obviously; this is fine if you're just passing known safe markup from within your code, but you should never pass anything entered by a user to this widget.)