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: I26f2df6d4657133a5c7e6ed85298aa843c1bdd73
Signed-off-by: Sean McGinnis <sean.mcginnis@gmail.com>

lower-constraints.txt

@@ -24,7 +24,6 @@ kombu==4.0.0
 linecache2==1.0.0
 MarkupSafe==1.0
 mccabe==0.2.1
-mock==2.0.0
 mox3==0.20.0
 msgpack-python==0.4.0
 netaddr==0.7.18

oslo_versionedobjects/fixture.py

@@ -27,10 +27,11 @@ import datetime
 import hashlib
 import inspect
 import logging
-import mock
-from oslo_utils import versionutils as vutils
+from unittest import mock
 
 import fixtures
+from oslo_utils import versionutils as vutils
+
 from oslo_versionedobjects import base
 from oslo_versionedobjects import fields
 

oslo_versionedobjects/test.py

@@ -25,8 +25,8 @@ eventlet.monkey_patch(os=False)  # noqa
 
 import functools
 import inspect
-import mock
 import os
+from unittest import mock
 
 import fixtures
 from oslo_concurrency import lockutils

oslo_versionedobjects/tests/test_exception.py

@@ -11,13 +11,11 @@
 #    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
 
 from oslo_versionedobjects import exception
 from oslo_versionedobjects import test
 
-import mock
-
-
 notifier = mock.Mock()
 
 

oslo_versionedobjects/tests/test_fields.py

@@ -14,10 +14,10 @@
 #    under the License.
 
 import datetime
+from unittest import mock
 import warnings
 
 import iso8601
-import mock
 import netaddr
 import testtools
 

oslo_versionedobjects/tests/test_fixture.py

@@ -17,9 +17,9 @@ import copy
 import datetime
 import hashlib
 import inspect
+from unittest import mock
 
 import iso8601
-import mock
 
 from oslo_versionedobjects import base
 from oslo_versionedobjects import exception

oslo_versionedobjects/tests/test_objects.py

@@ -17,8 +17,8 @@ import datetime
 import jsonschema
 import logging
 import pytz
+from unittest import mock
 
-import mock
 from oslo_context import context
 from oslo_serialization import jsonutils
 from oslo_utils import timeutils

test-requirements.txt

@@ -8,7 +8,6 @@ coverage!=4.4,>=4.0 # Apache-2.0
 jsonschema>=2.6.0 # MIT
 stestr>=2.0.0 # Apache-2.0
 
-mock>=2.0.0 # BSD
 fixtures>=3.0.0 # Apache-2.0/BSD
 
 # Bandit security code scanner