A recent IRC conversation [1] discussed that there are generally no tests for the placement handler code (the wsgi methods that respond to each URI and HTTP method). This change adds a paragraph to point out that this is mostly intentional and that when they get complex it would be a good idea to extract a method. [1] http://eavesdrop.openstack.org/irclogs/%23openstack-nova/%23openstack-nova.2018-03-28.log.html#t2018-03-28T13:00:40 Change-Id: I09774c123068e42e6a828fc37455dc5d374486b9