Add warnings override for unittest in the docs
Add warnings override for unittest in the docs

Unittest supresses warning filters unless `-Wd` flag is supplied and
this will result in test failures in python 3.5+.

zackw/pelican,ehashman/pelican,avaris/pelican,lucasplus/pelican,Rogdham/pelican,douglaskastle/pelican,Rogdham/pelican,ingwinlu/pelican,Scheirle/pelican,ehashman/pelican,farseerfc/pelican,avaris/pelican,zackw/pelican,Scheirle/pelican,farseerfc/pelican,getpelican/pelican,getpelican/pelican,iKevinY/pelican,talha131/pelican,talha131/pelican,zackw/pelican,douglaskastle/pelican,douglaskastle/pelican,lucasplus/pelican,Rogdham/pelican,ehashman/pelican,ingwinlu/pelican,lucasplus/pelican,Scheirle/pelican,iKevinY/pelican