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: I9bf0a8fbb7b4f22aa2f5b5ed0836d11cac27552b
Signed-off-by: Sean McGinnis <sean.mcginnis@gmail.com>

cloudkittyclient/tests/unit/v1/test_hashmap.py

@@ -13,7 +13,7 @@
 #    License for the specific language governing permissions and limitations
 #    under the License.
 #
-import mock
+from unittest import mock
 
 from cloudkittyclient import exc
 from cloudkittyclient.tests.unit.v1 import base

cloudkittyclient/tests/unit/v1/test_report_cli.py

@@ -13,7 +13,7 @@
 #    under the License.
 #
 import collections
-import mock
+from unittest import mock
 
 from cloudkittyclient.tests.unit.v1 import base
 from cloudkittyclient.v1 import report_cli

cloudkittyclient/tests/utils.py

@@ -12,12 +12,13 @@
 #    WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
 #    License for the specific language governing permissions and limitations
 #    under the License.
+from unittest import mock
+
 import fixtures
 import testtools
 
 from keystoneauth1 import adapter
 from keystoneauth1 import session
-import mock
 
 
 class BaseTestCase(testtools.TestCase):

test-requirements.txt

@@ -8,5 +8,4 @@ coverage>=4.0,!=4.4 # Apache-2.0
 python-subunit>=0.0.18 # Apache-2.0/BSD
 oslotest>=1.10.0 # Apache-2.0
 stestr>=2.0 # Apache-2.0
-mock>=2.0 # BSD
 python-openstackclient>=3.14 # Apache-2.0