Use testtools instead of unittest or unittest2.

As part of the move towards testr and parallel test running, we
start to use testtools and fixtures to make the test suite
resilient and more pedantic.

Part of blueprint grizzly-testtools

Change-Id: I90250de9fe21237db34f6a50b89b15863e270aa5

quantum/tests/unit/test_linux_dhcp.py

@@ -17,10 +17,10 @@
 
 import os
 import socket
-import unittest2 as unittest
 
 import mock
 from oslo.config import cfg
+import testtools
 
 from quantum.agent.common import config
 from quantum.agent.linux import dhcp
@@ -134,7 +134,7 @@ class FakeV4NoGatewayNetwork:
     ports = [FakePort1()]
 
 
-class TestDhcpBase(unittest.TestCase):
+class TestDhcpBase(testtools.TestCase):
     def test_base_abc_error(self):
         self.assertRaises(TypeError, dhcp.DhcpBase, None)
 
@@ -195,8 +195,9 @@ class LocalChild(dhcp.DhcpLocalProcess):
         self.called.append('spawn')
 
 
-class TestBase(unittest.TestCase):
+class TestBase(testtools.TestCase):
     def setUp(self):
+        super(TestBase, self).setUp()
         root = os.path.dirname(os.path.dirname(__file__))
         args = ['--config-file',
                 os.path.join(root, 'etc', 'quantum.conf.test')]
@@ -213,13 +214,11 @@ class TestBase(unittest.TestCase):
 
         self.replace_p = mock.patch('quantum.agent.linux.dhcp.replace_file')
         self.execute_p = mock.patch('quantum.agent.linux.utils.execute')
+        self.addCleanup(self.execute_p.stop)
         self.safe = self.replace_p.start()
+        self.addCleanup(self.replace_p.stop)
         self.execute = self.execute_p.start()
 
-    def tearDown(self):
-        self.execute_p.stop()
-        self.replace_p.stop()
-
 
 class TestDhcpLocalProcess(TestBase):
     def test_active(self):