Django 2.0 support

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 depreacted in Django 1.10:
https://docs.djangoproject.com/en/2.0/releases/1.10/#id3

Add py35dj20 job to test Django 2.0 integration.
Also drops py27dj110 from tox.ini as horizon droped
Django 1.10 support in Rocky.

Change-Id: Ieb4364d9c46f126d4fa797b42f7602fb73f33a0f

.zuul.yaml

@@ -4,8 +4,14 @@
         - openstack-tox-lower-constraints:
             required-projects:
               - openstack/horizon
+        - horizon-openstack-tox-py35dj20:
+            required-projects:
+              - openstack/horizon
     gate:
       jobs:
         - openstack-tox-lower-constraints:
             required-projects:
               - openstack/horizon
+        - horizon-openstack-tox-py35dj20:
+            required-projects:
+              - openstack/horizon

neutron_vpnaas_dashboard/dashboards/project/vpn/forms.py

@@ -14,7 +14,7 @@
 
 import logging
 
-from django.core.urlresolvers import reverse
+from django.urls import reverse
 from django.utils.translation import ugettext_lazy as _
 
 from horizon import exceptions

neutron_vpnaas_dashboard/dashboards/project/vpn/tables.py

@@ -13,8 +13,8 @@
 #    under the License.
 
 
-from django.core.urlresolvers import reverse
 from django import template
+from django.urls import reverse
 from django.utils.translation import pgettext_lazy
 from django.utils.translation import ugettext_lazy as _
 from django.utils.translation import ungettext_lazy

neutron_vpnaas_dashboard/dashboards/project/vpn/tests.py

@@ -12,7 +12,7 @@
 #    License for the specific language governing permissions and limitations
 #    under the License.
 
-from django.core.urlresolvers import reverse
+from django.urls import reverse
 
 from horizon.workflows import views
 

neutron_vpnaas_dashboard/dashboards/project/vpn/views.py

@@ -12,8 +12,8 @@
 #    License for the specific language governing permissions and limitations
 #    under the License.
 
-from django.core.urlresolvers import reverse
-from django.core.urlresolvers import reverse_lazy
+from django.urls import reverse
+from django.urls import reverse_lazy
 from django.utils.translation import ugettext_lazy as _
 
 from horizon import exceptions

releasenotes/notes/django2-support-ef2f2bd52a8bb63f.yaml

@@ -0,0 +1,6 @@
+---
+upgrade:
+  - |
+    Supported django versions are chagned aligning with the supported versions
+    by horizon. Django 1.11 and 2.0 are supported now. Django 1.8 to 1.10 are
+    no longer supported.

tox.ini

@@ -35,10 +35,10 @@ commands =
   coverage xml --omit '.tox/cover/*' -o 'cover/coverage.xml'
   coverage html --omit '.tox/cover/*' -d 'cover/htmlcov'
 
-[testenv:py27dj110]
-basepython = python2.7
+[testenv:py35dj20]
+basepython = python3.5
 commands =
-  pip install django>=1.10,<1.11
+  pip install django>=2.0,<2.1
   {[unit_tests]commands}
 
 [testenv:docs]