Release oslo.utils 4.0.0

This version officially drop the python 2 support so we release a major
version of oslo.utils to inform user that we break
the backward compatibility.

OpenStack is dropping the py2.7 support in ussuri cycle.

Complete discussion & schedule can be found in
-
http://lists.openstack.org/pipermail/openstack-discuss/2019-October/010142.html
- https://etherpad.openstack.org/p/drop-python2-support

Ussuri Communtiy-wide goal:
https://governance.openstack.org/tc/goals/selected/ussuri/drop-py27.html

Change-Id: Icffedb3ddd774bc9420e13875de2e5310d82b0f5

deliverables/ussuri/oslo.utils.yaml

@@ -15,3 +15,7 @@ releases:
     projects:
       - repo: openstack/oslo.utils
         hash: 577da7f00b36f23a95c0fa9beb6c4c702ad82f92
+  - version: 4.0.0
+    projects:
+      - repo: openstack/oslo.utils
+        hash: 18685083414cc247bb96f656a65e6b8c7f989ce0