tests: Use unittest.mock if available

Author: jleclanche

tests/test_oauth2_backends.py

@@ -1,6 +1,9 @@
 import json
 
-import mock
+try:
+    from unittest import mock
+except ImportError:
+    import mock
 
 from django.test import RequestFactory, TestCase
 

tests/test_oauth2_validators.py

@@ -1,6 +1,9 @@
 import datetime
 
-import mock
+try:
+    from unittest import mock
+except ImportError:
+    import mock
 
 from django.contrib.auth import get_user_model
 from django.test import TransactionTestCase