Use unittest.mock instead of mock

The mock third party library was needed for mock support in py2
runtimes. Since we now only support py36 and later, we can use the
standard lib unittest.mock module instead.

Change-Id: Id4029239c345655ea7ffc90b5969b29b47a84955

test-requirements.txt

@@ -9,7 +9,6 @@
 #
 charm-tools>=2.4.4
 requests>=2.18.4
-mock>=1.2
 flake8>=2.2.4,<=2.4.1
 stestr>=2.2.0
 coverage>=4.5.2

unit_tests/test_actions.py

@@ -18,12 +18,12 @@ import sys
 import tempfile
 import unittest
 
-import mock
+from unittest import mock
 import yaml
 
 from unit_tests.test_utils import CharmTestCase
 
-from mock import patch, MagicMock
+from unittest.mock import patch, MagicMock
 
 # python-apt is not installed as part of test-requirements but is imported by
 # some charmhelpers modules so create a fake import.

unit_tests/test_actions_openstack_upgrade.py

@@ -15,7 +15,7 @@
 import os
 import sys
 
-from mock import patch, MagicMock
+from unittest.mock import patch, MagicMock
 
 os.environ['JUJU_UNIT_NAME'] = 'swift-storage'
 

unit_tests/test_check_swift_storage.py

@@ -17,7 +17,7 @@ import sys
 import unittest
 import urllib
 
-from mock import (
+from unittest.mock import (
     patch,
     mock_open,
     MagicMock,

unit_tests/test_misc_utils.py

@@ -17,7 +17,7 @@ import tempfile
 import unittest
 import shutil
 
-from mock import patch
+from unittest.mock import patch
 
 from lib.misc_utils import ensure_block_device
 

unit_tests/test_swift_storage_context.py

@@ -12,7 +12,7 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-from mock import MagicMock
+from unittest.mock import MagicMock
 
 from unit_tests.test_utils import CharmTestCase, patch_open
 

unit_tests/test_swift_storage_relations.py

@@ -12,7 +12,7 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-from mock import patch
+from unittest.mock import patch
 import json
 import os
 import tempfile

unit_tests/test_swift_storage_utils.py

@@ -13,7 +13,7 @@
 # limitations under the License.
 
 from collections import namedtuple
-from mock import call, patch, MagicMock
+from unittest.mock import call, patch, MagicMock
 import shutil
 import tempfile
 

unit_tests/test_templates.py

@@ -12,7 +12,7 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-import mock
+from unittest import mock
 import unittest
 
 from jinja2 import Environment

unit_tests/test_utils.py

@@ -19,7 +19,7 @@ import unittest
 import yaml
 
 from contextlib import contextmanager
-from mock import MagicMock, patch
+from unittest.mock import MagicMock, patch
 
 
 def load_config():