Create Authentication Plugins

Provides the framework for creating authentication plugins and using
them from a session object.

To allow this system to co-exist with the original client there is a bit
of a hack. The client object itself is now also an authentication
plugin, that supports the original client pattern. If a client is
created without a session object then that session object uses the
client as it's authentication plugin.

Change-Id: I682c8dcd3705148aaa804a91f4ed48a5b74bdc12
blueprint: auth-plugins

test_session.py

@@ -17,6 +17,7 @@ import httpretty
 import mock
 import requests
 
+from keystoneclient.auth import base
 from keystoneclient import exceptions
 from keystoneclient import session as client_session
 from keystoneclient.tests import utils
@@ -252,3 +253,47 @@ class ConstructSessionFromArgsTests(utils.TestCase):
             args = {key: value}
             self.assertEqual(getattr(self._s(args), key), value)
             self.assertNotIn(key, args)
+
+
+class AuthPlugin(base.BaseAuthPlugin):
+    """Very simple debug authentication plugin.
+
+    Takes Parameters such that it can throw exceptions at the right times.
+    """
+
+    TEST_TOKEN = 'aToken'
+
+    def __init__(self, token=TEST_TOKEN):
+        self.token = token
+
+    def get_token(self, session):
+        return self.token
+
+
+class SessionAuthTests(utils.TestCase):
+
+    TEST_URL = 'http://127.0.0.1:5000/'
+    TEST_JSON = {'hello': 'world'}
+
+    @httpretty.activate
+    def test_auth_plugin_default_with_plugin(self):
+        self.stub_url('GET', base_url=self.TEST_URL, json=self.TEST_JSON)
+
+        # if there is an auth_plugin then it should default to authenticated
+        auth = AuthPlugin()
+        sess = client_session.Session(auth=auth)
+        resp = sess.get(self.TEST_URL)
+        self.assertDictEqual(resp.json(), self.TEST_JSON)
+
+        self.assertRequestHeaderEqual('X-Auth-Token', AuthPlugin.TEST_TOKEN)
+
+    @httpretty.activate
+    def test_auth_plugin_disable(self):
+        self.stub_url('GET', base_url=self.TEST_URL, json=self.TEST_JSON)
+
+        auth = AuthPlugin()
+        sess = client_session.Session(auth=auth)
+        resp = sess.get(self.TEST_URL, authenticated=False)
+        self.assertDictEqual(resp.json(), self.TEST_JSON)
+
+        self.assertRequestHeaderEqual('X-Auth-Token', None)