Python2: Add mock and unittest2 test dependencies

* unittest.mock was added in Python 3.3 standard library: use
  external 'mock' module, backport for Python 2.7
* assertRaisesRegex() method was added to Python 3.2 unittest module:
  use external 'unitttest2' backport for Python 2.7 to not have to
  rewrite unit tests just because of Python 2.7

Both added dependencies are specific to Python 2.7 and have no impact
on Python 3.

Related-Bug: 1726399
Change-Id: Ieb32e85d6f40f9b7bed5ba99900be2432d18da9e

ospurge/tests/__init__.py

@@ -0,0 +1,9 @@
+try:
+    from unittest import mock   # Python 3.3+
+except ImportError:
+    import mock  # noqa: Python 2.7
+
+try:
+    import unittest2 as unittest   # Python 2.7
+except ImportError:
+    import unittest   # noqa

ospurge/tests/resources/test_base.py

@@ -13,11 +13,11 @@ import time
 from typing import Any
 from typing import Dict
 from typing import Iterable
-import unittest
-from unittest import mock
 
 from ospurge import exceptions
 from ospurge.resources import base
+from ospurge.tests import mock
+from ospurge.tests import unittest
 
 
 def generate_timeout_series(timeout):

ospurge/tests/resources/test_cinder.py

@@ -10,11 +10,11 @@
 #  License for the specific language governing permissions and limitations
 #  under the License.
 import unittest
-from unittest import mock
 
 import shade
 
 from ospurge.resources import cinder
+from ospurge.tests import mock
 
 
 class TestBackups(unittest.TestCase):

ospurge/tests/resources/test_glance.py

@@ -10,11 +10,11 @@
 #  License for the specific language governing permissions and limitations
 #  under the License.
 import unittest
-from unittest import mock
 
 import shade
 
 from ospurge.resources import glance
+from ospurge.tests import mock
 
 
 class TestListImagesMixin(unittest.TestCase):

ospurge/tests/resources/test_neutron.py

@@ -10,11 +10,11 @@
 #  License for the specific language governing permissions and limitations
 #  under the License.
 import unittest
-from unittest import mock
 
 import shade
 
 from ospurge.resources import neutron
+from ospurge.tests import mock
 
 
 class TestFloatingIPs(unittest.TestCase):

ospurge/tests/resources/test_nova.py

@@ -10,11 +10,11 @@
 #  License for the specific language governing permissions and limitations
 #  under the License.
 import unittest
-from unittest import mock
 
 import shade
 
 from ospurge.resources import nova
+from ospurge.tests import mock
 
 
 class TestServers(unittest.TestCase):

ospurge/tests/resources/test_swift.py

@@ -10,11 +10,11 @@
 #  License for the specific language governing permissions and limitations
 #  under the License.
 import unittest
-from unittest import mock
 
 import shade
 
 from ospurge.resources import swift
+from ospurge.tests import mock
 
 
 class TestListObjectsMixin(unittest.TestCase):

ospurge/tests/test_main.py

@@ -13,13 +13,13 @@ import argparse
 import logging
 import types
 import unittest
-from unittest import mock
 
 import shade.exc
 
 from ospurge import exceptions
 from ospurge import main
 from ospurge.resources.base import ServiceResource
+from ospurge.tests import mock
 from ospurge import utils
 
 

ospurge/tests/test_utils.py

@@ -12,11 +12,11 @@
 import logging
 import typing
 import unittest
-from unittest import mock
 
 import shade
 
 from ospurge.resources.base import ServiceResource
+from ospurge.tests import mock
 from ospurge import utils
 
 

test-requirements.txt

@@ -5,3 +5,7 @@ hacking>=0.12.0,<0.13  # Apache-2.0
 openstackdocstheme>=1.5.0  # Apache-2.0
 sphinx>=1.2.1,!=1.3b1,<1.4  # BSD
 testrepository>=0.0.18  # Apache-2.0/BSD
+
+# Python 2.7 dependencies
+mock; python_version < '3.0'
+unittest2; python_version < '3.0'