Avoid meaningless comparison that leads to a TypeError

The "requests" module tries to do this comparison in raise_for_status():

    400 <= self.status_code < 500

with "self.status_code" being "None". In Python2, it's a valid comparison, but
in Python3, it triggers a TypeError. We fix it by giving a valid default value
to "self.status_code".

Change-Id: I9ea9ecfb698546a7f6526464aa528441bb7c1ccd

keystoneclient/tests/utils.py

@@ -109,7 +109,7 @@ class TestResponse(requests.Response):
         self._text = None
         super(TestResponse, self).__init__()
         if isinstance(data, dict):
-            self.status_code = data.get('status_code', None)
+            self.status_code = data.get('status_code', 200)
             headers = data.get('headers')
             if headers:
                 self.headers.update(headers)