Get rid of 3rd party mock

... by replacing it by the built-in unittest.mock .

Change-Id: Ie853237d5c59730353d5ea4a7e61888e066614be

diskimage_builder/block_device/tests/test_gpt.py

@@ -12,8 +12,8 @@
 
 import fixtures
 import logging
-import mock
 import os
+from unittest import mock
 
 import diskimage_builder.block_device.tests.test_config as tc
 

diskimage_builder/block_device/tests/test_lvm.py

@@ -12,7 +12,7 @@
 
 import copy
 import logging
-import mock
+from unittest import mock
 
 import diskimage_builder.block_device.tests.test_config as tc
 

diskimage_builder/block_device/tests/test_mbr.py

@@ -12,9 +12,9 @@
 
 import fixtures
 import logging
-import mock
 import os
 import subprocess
+from unittest import mock
 
 import diskimage_builder.block_device.tests.test_base as tb
 

diskimage_builder/block_device/tests/test_mount_order.py

@@ -12,8 +12,8 @@
 
 import functools
 import logging
-import mock
 import os
+from unittest import mock
 
 import diskimage_builder.block_device.tests.test_config as tc
 

diskimage_builder/elements/growvols/tests/test_growvols.py

@@ -12,9 +12,10 @@
 #    License for the specific language governing permissions and limitations
 #    under the License.
 import importlib
-import mock
 import os
 import sys
+from unittest import mock
+
 from oslotest import base
 
 

diskimage_builder/elements/package-installs/tests/test_package_squash.py

@@ -14,9 +14,9 @@
 import collections
 import functools
 import importlib
-import mock
 import os
 import sys
+from unittest import mock
 
 from oslotest import base
 from testtools.matchers import Mismatch

diskimage_builder/tests/test_diskimage_builder.py

@@ -12,12 +12,13 @@
 #    License for the specific language governing permissions and limitations
 #    under the License.
 
-import jsonschema
-import mock
+import os
 import subprocess
 import tempfile
+from unittest import mock
+
+import jsonschema
 import testtools
-import os
 import yaml
 
 from diskimage_builder import diskimage_builder as dib

requirements.txt

@@ -1,7 +1,3 @@
-# The order of packages is significant, because pip processes them in the order
-# of appearance. Changing the order has an impact on the overall integration
-# process, which may cause wedges in the gate later.
-
 networkx>=2.3.0 # BSD
 pbr!=2.1.0,>=2.0.0 # Apache-2.0
 PyYAML>=3.12 # MIT

test-requirements.txt

@@ -1,11 +1,6 @@
-# The order of packages is significant, because pip processes them in the order
-# of appearance. Changing the order has an impact on the overall integration
-# process, which may cause wedges in the gate later.
-
 pylint>=1.7.1 #GPLv2
 
 fixtures>=3.0.0 # Apache-2.0/BSD
-mock>=2.0.0 # BSD
 oslotest>=3.2.0 # Apache-2.0
 stestr>=2.0.0 # Apache-2.0
 testtools>=2.2.0 # MIT