Update lockutils from oslo-incubator

This commit updates lockutils from oslo incubator which adds a
LockFixture class. This also converts the tempest LockFixture to wrap
the fixture from oslo.

Change-Id: I4f5007109fa6ceff868c23d55d9962f9d703bb1f

tempest/common/tempest_fixtures.py

@@ -15,16 +15,9 @@
 #    License for the specific language governing permissions and limitations
 #    under the License.
 
-import fixtures
-
 from tempest.openstack.common import lockutils
 
 
-class LockFixture(fixtures.Fixture):
+class LockFixture(lockutils.LockFixture):
     def __init__(self, name):
-        self.mgr = lockutils.lock(name, 'tempest-', True)
-
-    def setUp(self):
-        super(LockFixture, self).setUp()
-        self.addCleanup(self.mgr.__exit__, None, None, None)
-        self.mgr.__enter__()
+        super(LockFixture, self).__init__(name, 'tempest-')

tempest/openstack/common/lockutils.py

@@ -24,6 +24,7 @@ import threading
 import time
 import weakref
 
+import fixtures
 from oslo.config import cfg
 
 from tempest.openstack.common import fileutils
@@ -275,3 +276,36 @@ def synchronized_with_prefix(lock_file_prefix):
     """
 
     return functools.partial(synchronized, lock_file_prefix=lock_file_prefix)
+
+
+class LockFixture(fixtures.Fixture):
+    """External locking fixture.
+
+    This fixture is basically an alternative to the synchronized decorator with
+    the external flag so that tearDowns and addCleanups will be included in
+    the lock context for locking between tests. The fixture is recommended to
+    be the first line in a test method, like so::
+
+        def test_method(self):
+            self.useFixture(LockFixture)
+                ...
+
+    or the first line in setUp if all the test methods in the class are
+    required to be serialized. Something like::
+
+        class TestCase(testtools.testcase):
+            def setUp(self):
+                self.useFixture(LockFixture)
+                super(TestCase, self).setUp()
+                    ...
+
+    This is because addCleanups are put on a LIFO queue that gets run after the
+    test method exits. (either by completing or raising an exception)
+    """
+    def __init__(self, name, lock_file_prefix=None):
+        self.mgr = lock(name, lock_file_prefix, True)
+
+    def setUp(self):
+        super(LockFixture, self).setUp()
+        self.addCleanup(self.mgr.__exit__, None, None, None)
+        self.mgr.__enter__()