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: Ie36f12a4a6dd3c06b9ffd9bfb7bbb0106311820f

test-requirements.txt

@@ -6,7 +6,6 @@
 hacking>=3.0.1,<3.1.0 # Apache-2.0
 bashate>=0.5.1 # Apache-2.0
 coverage!=4.4,>=4.0 # Apache-2.0
-mock>=2.0.0 # BSD
 virtualenv>=14.0.6 # MIT
 # TODO(noonedeadpunk) Upgrade linters versions and drop pycodestyle
 # once we stop doing linters check for the integrated repo with

tests/test_filesystem.py

@@ -13,12 +13,12 @@
 # under the License.
 #
 
-import mock
 import os
 from os import path
 from osa_toolkit import filesystem as fs
 import sys
 import unittest
+from unittest import mock
 
 from test_inventory import cleanup
 from test_inventory import get_inventory

tests/test_inventory.py

@@ -13,7 +13,6 @@
 import collections
 import copy
 import json
-import mock
 import os
 from os import path
 try:
@@ -22,6 +21,7 @@ except ImportError:
     import queue as Queue
 import sys
 import unittest
+from unittest import mock
 import warnings
 import yaml