Deprecate create v3 Client without session

There was a comment to deprecate creating a v3 Client
without a session.

bp deprecations

Change-Id: Ifc3fa9ffef12554646ca80f04527de757df3aa95

keystoneclient/tests/unit/v3/utils.py

@@ -129,6 +129,9 @@ class TestCase(UnauthenticatedTestCase):
 
     def setUp(self):
         super(TestCase, self).setUp()
+
+        # Creating a Client not using session is deprecated.
+        with self.deprecations.expect_deprecations_here():
             self.client = client.Client(token=self.TEST_TOKEN,
                                         auth_url=self.TEST_URL,
                                         endpoint=self.TEST_URL)

keystoneclient/v3/client.py

@@ -14,6 +14,7 @@
 #    under the License.
 
 import logging
+import warnings
 
 from oslo_serialization import jsonutils
 
@@ -83,6 +84,12 @@ class Client(httpclient.HTTPClient):
     :param integer timeout: Allows customization of the timeout for client
                             http requests. (optional)
 
+    .. warning::
+
+        Constructing an instance of this class without a session is
+        deprecated as of the 1.7.0 release and will be removed in the
+        2.0.0 release.
+
     Example::
 
         >>> from keystoneclient.v3 import client
@@ -182,6 +189,13 @@ EndpointPolicyManager`
         """Initialize a new client for the Keystone v3 API."""
         super(Client, self).__init__(**kwargs)
 
+        if not kwargs.get('session'):
+            warnings.warn(
+                'Constructing an instance of the '
+                'keystoneclient.v3.client.Client class without a session is '
+                'deprecated as of the 1.7.0 release and may be removed in '
+                'the 2.0.0 release.', DeprecationWarning)
+
         self.auth = auth.AuthManager(self._adapter)
         self.credentials = credentials.CredentialManager(self._adapter)
         self.ec2 = ec2.EC2Manager(self._adapter)