Ensure run_watchers called from mixin, not base class

A new mixin was introduced to share run_watchers across drivers,
but the base class's run_watchers() currently gets called instead,
resulting in a NotImplemented error.

Change-Id: I5f23f63100a9c00837025b291cb1db0a5187a8e9
Closes-bug: #1470264

tooz/drivers/file.py

@@ -110,8 +110,8 @@ class FileLock(locking.Lock):
             LOG.warn("Unreleased lock %s garbage collected", self.name)
 
 
-class FileDriver(coordination.CoordinationDriver,
+class FileDriver(coordination._RunWatchersMixin,
-                 coordination._RunWatchersMixin):
+                 coordination.CoordinationDriver):
     """A file based driver.
 
     This driver uses files and directories (and associated file locks) to

tooz/drivers/memcached.py

@@ -114,8 +114,8 @@ class MemcachedLock(locking.Lock):
         return self.coord.client.get(self.name)
 
 
-class MemcachedDriver(coordination.CoordinationDriver,
+class MemcachedDriver(coordination._RunWatchersMixin,
-                      coordination._RunWatchersMixin):
+                      coordination.CoordinationDriver):
     """A `memcached`_ based driver.
 
     This driver users `memcached`_ concepts to provide the coordination driver

tooz/drivers/redis.py

@@ -98,8 +98,8 @@ class RedisLock(locking.Lock):
                 self._lock.extend(self._lock.timeout)
 
 
-class RedisDriver(coordination.CoordinationDriver,
+class RedisDriver(coordination._RunWatchersMixin,
-                  coordination._RunWatchersMixin):
+                  coordination.CoordinationDriver):
     """Redis provides a few nice benefits that act as a poormans zookeeper.
 
     It **is** fully functional and implements all of the coordination

tooz/tests/test_memcache.py

@@ -69,3 +69,16 @@ class TestMemcacheDriverFailures(testcase.TestCase):
         coord.start()
         mock_client.set.side_effect = socket.timeout('timed-out')
         self.assertRaises(coordination.ToozConnectionError, coord.heartbeat)
+
+    @mock.patch('tooz.coordination._RunWatchersMixin.run_watchers',
+                autospec=True)
+    @mock.patch('pymemcache.client.PooledClient')
+    def test_client_run_watchers_mixin(self, mock_client_cls,
+                                       mock_run_watchers):
+        mock_client = mock.MagicMock()
+        mock_client_cls.return_value = mock_client
+        member_id = str(uuid.uuid4()).encode('ascii')
+        coord = coordination.get_coordinator(self.FAKE_URL, member_id)
+        coord.start()
+        coord.run_watchers()
+        self.assertTrue(mock_run_watchers.called)