Ensure that failing responses are logged

The boolean value of a failed response is False and so the way we
populate the log output does not work when the request failed.

When logging check that a response is not None rather than simply
checking it's boolean value.

Change-Id: I07fb46f156fdf8267fd3d4dc7c587cd604838d73
Closes-Bug: #1451625

keystoneclient/session.py

@@ -201,7 +201,7 @@ class Session(object):
         if not logger.isEnabledFor(logging.DEBUG):
             return
 
-        if response:
+        if response is not None:
             if not status_code:
                 status_code = response.status_code
             if not headers:

keystoneclient/tests/unit/test_session.py

@@ -174,6 +174,18 @@ class SessionTests(utils.TestCase):
             self.assertEqual(v, resp.headers[k])
             self.assertNotIn(v, self.logger.output)
 
+    def test_logs_failed_output(self):
+        """Test that output is logged even for failed requests"""
+
+        session = client_session.Session()
+        body = uuid.uuid4().hex
+
+        self.stub_url('GET', text=body, status_code=400)
+        resp = session.get(self.TEST_URL, raise_exc=False)
+
+        self.assertEqual(resp.status_code, 400)
+        self.assertIn(body, self.logger.output)
+
     def test_logging_cacerts(self):
         path_to_certs = '/path/to/certs'
         session = client_session.Session(verify=path_to_certs)