HTTPErrors do not contain the error message from the server

[crazyscientist]

When using the REST API, the Bugzilla client raises HTTPErrors without a response attribute.

E.g., when trying to create a bug with an already taken alias, the XMLRPC backend raises a Fault exception with a meaningful code number and string. The HTTPError raised by the REST backend only contains the generic HTTP status code and status message.

Whatever useful error message from the server is lost.

[crazyscientist]

FYI: This might be related to #171?

[crazyscientist]

I can confirm that #172 solves this problem 🙂

Duplicate of #171