py3: HTTPResponse has no 'dict' attribute in 'msg'
    
    There is no 'dict' attribute in 'msg', but 'msg' attribute is dict-like object
    in both py2/3, so it can be used instead.
    
    https://fedorahosted.org/freeipa/ticket/4985
    
    Reviewed-By: Christian Heimes <cheimes@redhat.com>
    Reviewed-By: Jan Cholasta <jcholast@redhat.com>