Deprecated the yamlutils module.

The pyyaml is now safe by default:

https://github.com/yaml/pyyaml/pull/74/files
https://access.redhat.com/security/cve/CVE-2017-18342

So the yamlutils is now useless. We can depracated it and then remove it.

Change-Id: I4ecb34eee942c714d09d2258db80f5b8d61dec89

oslo_serialization/yamlutils.py

@@ -18,9 +18,16 @@ of yaml manager in all the openstack projects.
 Use this module inside openstack projects to handle yaml securely and properly.
 """
 
+from debtcollector import removals
 import yaml
 
 
+removals.removed_module(
+    'oslo_serialization.yamlutils', version='3.0.0',
+    removal_version='4.0.0',
+    message='The oslo_serialization.yamlutils will be removed')
+
+
 def load(stream, is_safe=True):
     """Converts a YAML document to a Python object.
 

requirements.txt

@@ -13,3 +13,4 @@ msgpack>=0.5.2 # Apache-2.0
 oslo.utils>=3.33.0 # Apache-2.0
 pytz>=2013.6 # MIT
 PyYAML>=3.12 # MIT
+debtcollector>=1.2.0 # Apache-2.0