Issue deprecation message for the barbican CLI

The barbican CLI has been deprecated and users should use the openstack
unified CLI instead.

Change-Id: Ie78b2c913b1520f1df312ab7a11e0132f0c36d26

barbicanclient/barbican.py

@@ -17,8 +17,9 @@
 Command-line interface to the Barbican API.
 """
 
-import sys
 from collections import namedtuple
+import logging
+import sys
 
 from cliff import app
 from cliff import command
@@ -34,6 +35,9 @@ from barbicanclient import client
 from barbicanclient import version
 
 
+LOG = logging.getLogger(__name__)
+
+
 _DEFAULT_IDENTITY_API_VERSION = '3'
 _IDENTITY_API_VERSION_2 = ['2', '2.0']
 _IDENTITY_API_VERSION_3 = ['3']
@@ -335,6 +339,10 @@ class Barbican(app.App):
 
 
 def main(argv=sys.argv[1:]):
+    logging.basicConfig()
+    LOG.warning("This Barbican CLI interface has been deprecated and will be "
+                "removed in the O release. Please use the openstack unified "
+                "client instead.")
     barbican_app = Barbican()
     return barbican_app.run(argv)