Add a backport of Django 1.8's URLValidator.

Review Request #8978 — Created May 30, 2017 and submitted — Latest diff uploaded

Information

Djblets
release-0.9.x
50ef07d...

Reviewers

The URLValidator that ships with Django 1.6 is pretty basic, and doesn't
understand URLs that include credentials. This change adds a backport of the
Django 1.8 version, which does that plus more.

Used this in conjunction with a change in Review Board.