Use unittest.mock instead of third party mock

Now that we no longer support py27, we can use the standard library
unittest.mock module instead of the third party mock lib.

Change-Id: I017716842c61b814bbe16cc2b8788f160f4ad9cd
Signed-off-by: Sean McGinnis <sean.mcginnis@gmail.com>
diff --git a/patrole_tempest_plugin/tests/unit/fixtures.py b/patrole_tempest_plugin/tests/unit/fixtures.py
index 41afe9b..2ce1d08 100644
--- a/patrole_tempest_plugin/tests/unit/fixtures.py
+++ b/patrole_tempest_plugin/tests/unit/fixtures.py
@@ -15,9 +15,9 @@
 
 """Fixtures for Patrole tests."""
 from __future__ import absolute_import
+from unittest import mock
 
 import fixtures
-import mock
 import time
 
 from tempest.common import credentials_factory as credentials
diff --git a/patrole_tempest_plugin/tests/unit/test_policy_authority.py b/patrole_tempest_plugin/tests/unit/test_policy_authority.py
index 185e449..cdc9e15 100644
--- a/patrole_tempest_plugin/tests/unit/test_policy_authority.py
+++ b/patrole_tempest_plugin/tests/unit/test_policy_authority.py
@@ -13,8 +13,8 @@
 #    License for the specific language governing permissions and limitations
 #    under the License.
 
-import mock
 import os
+from unittest import mock
 
 from tempest import config
 
diff --git a/patrole_tempest_plugin/tests/unit/test_rbac_rule_validation.py b/patrole_tempest_plugin/tests/unit/test_rbac_rule_validation.py
index 5c4efff..2c7307e 100644
--- a/patrole_tempest_plugin/tests/unit/test_rbac_rule_validation.py
+++ b/patrole_tempest_plugin/tests/unit/test_rbac_rule_validation.py
@@ -13,9 +13,9 @@
 #    under the License.
 
 from __future__ import absolute_import
+from unittest import mock
 
 import functools
-import mock
 from oslo_config import cfg
 
 import fixtures
diff --git a/patrole_tempest_plugin/tests/unit/test_rbac_utils.py b/patrole_tempest_plugin/tests/unit/test_rbac_utils.py
index e84a56d..e61f798 100644
--- a/patrole_tempest_plugin/tests/unit/test_rbac_utils.py
+++ b/patrole_tempest_plugin/tests/unit/test_rbac_utils.py
@@ -13,8 +13,8 @@
 #    License for the specific language governing permissions and limitations
 #    under the License.
 
-import mock
 import testtools
+from unittest import mock
 
 from tempest.lib import exceptions as lib_exc