[1.5.X] Fixed #19230 -- Extended the handler403 documentation.
[1.5.X] Fixed #19230 -- Extended the handler403 documentation.

Backport of 0546794397130b1574a667d57667bd032bff78d3 from master.

Added a paragraph on how to use the PermissionDenied exception to create a 403
response and use handler403.

ccn-2m/django,hasadna/django,bliti/django-nonrel-1.5,ccn-2m/django,hasadna/django,hasadna/django,alx-eu/django,alx-eu/django,ccn-2m/django,alx-eu/django,bliti/django-nonrel-1.5,imtapps/django-imt-fork,imtapps/django-imt-fork,alx-eu/django,ccn-2m/django,imtapps/django-imt-fork,bliti/django-nonrel-1.5