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>

lower-constraints.txt

@@ -28,7 +28,6 @@ keystoneauth1==3.4.0
 linecache2==1.0.0
 MarkupSafe==1.0
 mccabe==0.2.1
-mock==2.0.0
 monotonic==1.4
 mox3==0.25.0
 msgpack==0.5.6

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

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
 

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

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
 

test-requirements.txt

@@ -3,7 +3,6 @@
 # process, which may cause wedges in the gate later.
 hacking>=3.0,<3.1.0 # Apache-2.0
 fixtures>=3.0.0 # Apache-2.0/BSD
-mock>=2.0.0 # BSD
 coverage!=4.4,>=4.0 # Apache-2.0
 nose>=1.3.7 # LGPL
 nosexcover>=1.0.10 # BSD