Merge servid-error-7355: Brief description

Author: exarkun, adiroiban

Reviewer: glyph

Fixes: #7355

Fix the Python 3 buildbots.

git-svn-id: svn://svn.twistedmatrix.com/svn/Twisted/trunk@43180 bbbe8e31-12d6-0310-92fd-ac37d47ddeeb