Fix response always being False

From requests.models.Response:
Returns True if :attr:`status_code` is less than 400.

We're using it wrong, so have changed it to "is not None"

Change-Id: I617e55d67d93f1e07f5192ba94dcc0997ba9e12f

openstack/exceptions.py

@@ -60,7 +60,7 @@ class HttpException(SDKException, _rex.HTTPError):
         # TODO(shade) Remove http_status parameter and the ability for response
         # to be None once we're not mocking Session everywhere.
         if not message:
-            if response:
+            if response is not None:
                 message = "{name}: {code}".format(
                     name=self.__class__.__name__,
                     code=response.status_code)
@@ -72,7 +72,7 @@ class HttpException(SDKException, _rex.HTTPError):
         SDKException.__init__(self, message=message)
         _rex.HTTPError.__init__(self, message, response=response)
 
-        if response:
+        if response is not None:
             self.request_id = response.headers.get('x-openstack-request-id')
             self.status_code = response.status_code
         else:

openstack/tests/unit/cloud/test_image.py

@@ -650,7 +650,7 @@ class TestImage(BaseTestImage):
         ]
         mock_image_client.post.return_value = ret
         mock_image_client.put.side_effect = exc.OpenStackCloudHTTPError(
-            "Some error", {})
+            "Some error")
         self.assertRaises(
             exc.OpenStackCloudHTTPError,
             self._call_create_image,
@@ -724,7 +724,7 @@ class TestImage(BaseTestImage):
         ]
         mock_image_client.post.return_value = ret
         mock_image_client.put.side_effect = exc.OpenStackCloudHTTPError(
-            "Some error", {})
+            "Some error")
         self.assertRaises(
             exc.OpenStackCloudHTTPError,
             self._call_create_image,