Correct docs usage of keystoneauth1 session

keystoneclient.session has been long deprecated in favor of
keystoneauth1.session. This change corrects entries in the
documentation to use the correct library's session.

Change-Id: I92226c9407ff77839a96cc9476f01eb7acf5c379

README.rst

@@ -38,7 +38,7 @@ with keystone authentication:
 .. code:: python
 
     >>> from keystoneclient.auth import identity
-    >>> from keystoneclient import session
+    >>> from keystoneauth1 import session
     >>> from barbicanclient import client
 
     >>> # We'll use Keystone API v3 for authentication

barbicanclient/client.py

@@ -123,7 +123,7 @@ def Client(version=None, session=None, *args, **kwargs):
         """Barbican client used to interact with barbican service.
 
         :param version: The API version to use.
-        :param session: An instance of keystoneclient.session.Session that
+        :param session: An instance of keystoneauth1.session.Session that
             can be either authenticated, or not authenticated.  When using
             a non-authenticated Session, you must provide some additional
             parameters.  When no session is provided it will default to a

barbicanclient/v1/client.py

@@ -30,7 +30,7 @@ class Client(object):
     def __init__(self, session=None, *args, **kwargs):
         """Barbican client object used to interact with barbican service.
 
-        :param session: An instance of keystoneclient.session.Session that
+        :param session: An instance of keystoneauth1.session.Session that
             can be either authenticated, or not authenticated.  When using
             a non-authenticated Session, you must provide some additional
             parameters.  When no session is provided it will default to a