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: Ib2653b7490922c10763321572390fca3aaeafa33
Signed-off-by: Sean McGinnis <sean.mcginnis@gmail.com>

paunch/tests/test_builder_base.py

@@ -15,8 +15,8 @@
 import collections
 import inspect
 import json
-import mock
 import tenacity
+from unittest import mock
 
 from paunch.builder import base as basebuilder
 from paunch.builder import compose1

paunch/tests/test_builder_compose1.py

@@ -12,7 +12,7 @@
 # License for the specific language governing permissions and limitations
 # under the License.
 
-import mock
+from unittest import mock
 
 from paunch.builder import compose1
 from paunch.tests import test_builder_base as tbb

paunch/tests/test_builder_podman.py

@@ -12,7 +12,7 @@
 # License for the specific language governing permissions and limitations
 # under the License.
 
-import mock
+from unittest import mock
 
 from paunch.builder import podman
 from paunch.tests import test_builder_base as base

paunch/tests/test_paunch.py

@@ -12,7 +12,7 @@
 # License for the specific language governing permissions and limitations
 # under the License.
 
-import mock
+from unittest import mock
 
 import paunch
 from paunch.tests import base

paunch/tests/test_runner.py

@@ -12,8 +12,8 @@
 # License for the specific language governing permissions and limitations
 # under the License.
 
-import mock
 from testtools import matchers
+from unittest import mock
 
 from paunch import runner
 from paunch.tests import base

paunch/tests/test_utils_common.py

@@ -13,7 +13,7 @@
 # License for the specific language governing permissions and limitations
 # under the License.
 
-import mock
+from unittest import mock
 
 from paunch.tests import base
 from paunch.utils import common

paunch/tests/test_utils_systemctl.py

@@ -13,7 +13,7 @@
 # License for the specific language governing permissions and limitations
 # under the License.
 
-import mock
+from unittest import mock
 
 from paunch.tests import base
 from paunch.utils import systemctl

paunch/tests/test_utils_systemd.py

@@ -13,9 +13,9 @@
 # License for the specific language governing permissions and limitations
 # under the License.
 
-import mock
 import os
 import tempfile
+from unittest import mock
 
 from paunch.tests import base
 from paunch.utils import systemd