Replace django.core.urlresolves with django.urls
(In Django 2.0) The django.core.urlresolvers module is removed
in favor of its new location, django.urls.
It was deprecated in Django 1.10:
https://docs.djangoproject.com/en/2.0/releases/1.10/#id3
Add py35dj20 job to test Django 2.0 integration.
Change-Id: I6d2e38201387012ba9a02c4b0bd8377895a5919a
Fixed a lot of AttributeError: 'module' object has no attribute 'nested'
and F821 undefined name 'unicode' errors.
Change-Id: I79e73e27608ec6b76fd4ccf0ee9dcaf2ddf965ed
Closes-Bug: #1544499
