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: I5587ac8f603798aad27908d3bd6ed8ebb3a9c14e
Signed-off-by: Sean McGinnis <sean.mcginnis@gmail.com>

lower-constraints.txt

@@ -22,7 +22,6 @@ keystoneauth1==3.4.0
 linecache2==1.0.0
 MarkupSafe==1.0
 mccabe==0.2.1
-mock==2.0.0
 monotonic==1.4;python_version<'3.3'
 mox3==0.25.0
 msgpack==0.5.6

oslo_log/tests/unit/test_formatters.py

@@ -14,17 +14,17 @@
 
 """Unit Tests for oslo.log formatter"""
 
-import mock
-
 import logging
 import sys
+from unittest import mock
 
 from oslo_config import cfg
 from oslo_config import fixture as config_fixture
 from oslo_context import context
+from oslotest import base as test_base
+
 from oslo_log import formatters
 from oslo_log import log
-from oslotest import base as test_base
 
 
 def _fake_context():

oslo_log/tests/unit/test_helpers.py

@@ -10,10 +10,12 @@
 #    License for the specific language governing permissions and limitations
 #    under the License.
 
-import mock
-from oslo_log import helpers
+from unittest import mock
+
 from oslotest import base as test_base
 
+from oslo_log import helpers
+
 
 class LogHelpersTestCase(test_base.BaseTestCase):
 

oslo_log/tests/unit/test_log.py

@@ -31,9 +31,9 @@ except ImportError:
     syslog = None
 import tempfile
 import time
+from unittest import mock
 
 from dateutil import tz
-import mock
 from oslo_config import cfg
 from oslo_config import fixture as fixture_config  # noqa
 from oslo_context import context

oslo_log/tests/unit/test_rate_limit.py

@@ -14,8 +14,8 @@
 
 import io
 import logging
+from unittest import mock
 
-import mock
 from oslotest import base as test_base
 
 from oslo_log import rate_limit

oslo_log/tests/unit/test_versionutils.py

@@ -13,7 +13,8 @@
 #    License for the specific language governing permissions and limitations
 #    under the License.
 
-import mock
+from unittest import mock
+
 from oslotest import base as test_base
 from testtools import matchers
 

test-requirements.txt

@@ -6,7 +6,6 @@ hacking>=2.0.0,<2.1.0 # Apache-2.0
 
 stestr>=2.0.0 # Apache-2.0
 testtools>=2.3.0 # MIT
-mock>=2.0.0 # BSD
 oslotest>=3.3.0 # Apache-2.0
 
 coverage>=4.5.1 # Apache-2.0