Replace external mock with built-in unittest.mock

Now that stevedore does not support Python 2 anymore, there is no need
to ever use the external 'mock' package.  Python 3.3+ has it integrated
as 'unittest.mock', so just use that.

Change-Id: I28a50cac12670bb6987b4c7794a15e15aa1fe965
Signed-off-by: Michał Górny <mgorny@gentoo.org>

.travis.yml

@@ -6,7 +6,7 @@ python:
   - "pypy"
 install:
   - pip install flake8 --use-mirrors
-  - pip install nose mock --use-mirrors
+  - pip install nose --use-mirrors
   - pip install -q . --use-mirrors
 before_script:
   - flake8 stevedore setup.py

lower-constraints.txt

@@ -11,7 +11,6 @@ imagesize==0.7.1
 Jinja2==2.10
 linecache2==1.0.0
 MarkupSafe==1.0
-mock==2.0.0
 pbr==2.0.0
 Pygments==2.2.0
 python-mimeparse==1.6.0

stevedore/tests/test_callback.py

@@ -12,8 +12,9 @@
 
 """Tests for failure loading callback
 """
+from unittest import mock
+
 from testtools.matchers import GreaterThan
-import mock
 
 from stevedore import extension
 from stevedore import named

stevedore/tests/test_extension.py

@@ -14,8 +14,7 @@
 """
 
 import operator
-
+from unittest import mock
-import mock
 
 from stevedore import exception
 from stevedore import extension

stevedore/tests/test_named.py

@@ -10,11 +10,11 @@
 #  License for the specific language governing permissions and limitations
 #  under the License.
 
+from unittest import mock
+
 from stevedore import named
 from stevedore.tests import utils
 
-import mock
-
 
 class TestNamed(utils.TestCase):
     def test_named(self):

stevedore/tests/test_sphinxext.py

@@ -12,11 +12,12 @@
 """Tests for the sphinx extension
 """
 
+from unittest import mock
+
 from stevedore import extension
 from stevedore import sphinxext
 from stevedore.tests import utils
 
-import mock
 import pkg_resources
 
 

stevedore/tests/test_test_manager.py

@@ -10,7 +10,8 @@
 #  License for the specific language governing permissions and limitations
 #  under the License.
 
-from mock import Mock, sentinel
+from unittest.mock import Mock, sentinel
+
 from stevedore import (ExtensionManager, NamedExtensionManager, HookManager,
                        DriverManager, EnabledExtensionManager)
 from stevedore.dispatch import (DispatchExtensionManager,

test-requirements.txt

@@ -2,7 +2,6 @@
 # of appearance. Changing the order has an impact on the overall integration
 # process, which may cause wedges in the gate later.
 
-mock>=2.0.0 # BSD
 coverage!=4.4,>=4.0 # Apache-2.0
 stestr>=2.0.0 # Apache-2.0
 # sphinx is needed for testing the sphinxext module