[response] Add defaults to http response error (#117)

v3io/dataplane/response.py

@@ -22,7 +22,7 @@
 class HttpResponseError(Exception):
     """Exception raised on bad http status"""
 
-    def __init__(self, message, status_code):
+    def __init__(self, message="", status_code=None):
         super().__init__(message)
         self.status_code = status_code