Specifically in rendering shortcuts, template responses, and class-based
views that return template responses.

Also added a test for render_to_response(status=...) which was missing
from fdbfc980.

Thanks Tim and Carl for the review.

Refs #20104.

Refs #19076.

Thanks Gavin Wahl.

Added -n to sphinx builds to catch issues going forward.

Updated the most recent patch from @claudep to apply again and updated
the documentation location.

Many thanks to Daniel Greenfeld, James Aylett, Marc Tamlyn, Simon Williams, Danilo Bargen and Luke Plant for their work on this.