Deprecate zake driver because of unmaintained library

The zake library[1] was already archived a few years ago. It has had
no release for 7 years.

[1] https://github.com/yahoo/Zake
[2] https://pypi.org/project/zake/#history

Change-Id: I82d6cdeec2be4f69d325270f4cd74f2cafe9db55

releasenotes/notes/deprecate-zake-driver-eee8fcdfc5a88907.yaml

@@ -0,0 +1,5 @@
+---
+deprecations:
+  - |
+    The zake driver has been deprecated and will be removed in a future
+    release.

tooz/drivers/zake.py

@@ -12,6 +12,8 @@
 # License for the specific language governing permissions and limitations
 # under the License.
 
+import warnings
+
 from zake import fake_client
 from zake import fake_storage
 
@@ -47,6 +49,13 @@ class ZakeDriver(zookeeper.KazooDriver):
     fake_storage = fake_storage.FakeStorage(
         fake_client.k_threading.SequentialThreadingHandler())
 
+    def __init__(self, member_id, parsed_url, options):
+        super(ZakeDriver, self).__init__(member_id, parsed_url, options)
+        warnings.warn(
+            "The zake driver is deprecated, and will be removed in "
+            "a future release."
+        )
+
     @classmethod
     def _make_client(cls, parsed_url, options):
         if 'storage' in options: