Allow mock-based patching in shell tests

Added `patch` method that uses mock.patch (similar to `patchobject`)
  - NOTE: this shadows `testtools.TestCase.patch` method that uses
    simple monkey-patching in favor of mock-based patching,
    relevant comment added in the code.
Also oslotest dependency is added.

Change-Id: Ie4d25bc53decb308398eded350c81a90a257b254
Related-Bug: #1384511

heatclient/tests/test_shell.py

@@ -24,6 +24,7 @@ import fixtures
 import httpretty
 from keystoneclient.fixture import v2 as ks_v2_fixture
 from keystoneclient.fixture import v3 as ks_v3_fixture
+from oslotest import mockpatch
 import requests
 import tempfile
 import testscenarios
@@ -132,6 +133,12 @@ class TestCase(testtools.TestCase):
             keystone_client_fixtures.BASE_URL,
             body=keystone_client_fixtures.keystone_request_callback)
 
+    # NOTE(tlashchova): this overrides the testtools.TestCase.patch method
+    # that does simple monkey-patching in favor of mock's patching
+    def patch(self, target, **kwargs):
+        mockfixture = self.useFixture(mockpatch.Patch(target, **kwargs))
+        return mockfixture.mock
+
 
 class EnvVarTest(TestCase):
 

test-requirements.txt

@@ -11,6 +11,7 @@ httpretty>=0.8.0,!=0.8.1,!=0.8.2,!=0.8.3
 mock>=1.0
 mox3>=0.7.0
 oslosphinx>=2.2.0  # Apache-2.0
+oslotest>=1.2.0  # Apache-2.0
 sphinx>=1.1.2,!=1.2.0,!=1.3b1,<1.3
 testrepository>=0.0.18
 testscenarios>=0.4