[Django 1.9] Replace django.utils.unittest

This patch replaces django.utils.unittest with unittest.
https://docs.djangoproject.com/en/1.9/releases/1.7/#django-utils-unittest

Change-Id: Ifd6138c5afa4a3e952989bf9bb73076c51f1898b
Partially-implements: blueprint drop-dj17

horizon/test/helpers.py

@@ -20,6 +20,7 @@ import logging
 import os
 import socket
 import time
+import unittest
 
 from django.contrib.auth.middleware import AuthenticationMiddleware  # noqa
 from django.contrib.auth.models import Permission  # noqa
@@ -32,7 +33,6 @@ from django import http
 from django import test as django_test
 from django.test.client import RequestFactory  # noqa
 from django.utils.encoding import force_text
-from django.utils import unittest
 import six
 
 from django.contrib.staticfiles.testing \

horizon/test/tests/test_file_discovery.py

@@ -10,8 +10,8 @@
 # License for the specific language governing permissions and limitations
 # under the License.
 
-from django.utils import unittest
 from horizon.utils import file_discovery as fd
+import unittest
 
 base_path = 'some_root/fake_static_files/'
 

openstack_dashboard/dashboards/identity/projects/tests.py

@@ -16,13 +16,13 @@ import copy
 import datetime
 import logging
 import os
+import unittest
 
 import django
 from django.core.urlresolvers import reverse
 from django import http
 from django.test.utils import override_settings
 from django.utils import timezone
-from django.utils import unittest
 
 from mox3.mox import IgnoreArg  # noqa
 from mox3.mox import IsA  # noqa

openstack_dashboard/test/helpers.py

@@ -20,7 +20,7 @@ import collections
 import copy
 from functools import wraps  # noqa
 import os
-
+import unittest
 
 from ceilometerclient.v2 import client as ceilometer_client
 from cinderclient import client as cinder_client
@@ -31,7 +31,6 @@ from django.core import urlresolvers
 from django.test.client import RequestFactory  # noqa
 from django.test import utils as django_test_utils
 from django.utils.importlib import import_module  # noqa
-from django.utils import unittest
 import glanceclient
 from heatclient import client as heat_client
 import httplib2