pym/_emerge/depgrapgh.py: Fix bug 518968

Fixes commit: 1a00ddf5fb089724a127c8dc72d63f10ae72abbf
Author: Alexander Berntsen <bernalex@gentoo.org> (Thu 08 May 2014 08:47:58 AM PDT)
Subject: emerge: Implement "--alert"

self.query was not assigned using the correct UserQuery instance.
self.uq was not used by anything anywhere.  This patch consolidates it to the one initialized instance in 1 line of code.
Original bug reproduced and fixed by: Mike Gilbert <floppym@gentoo.org>