'Add json_error_formatter to any webob HTTPExceptions.'

def call_func(self, req, *args, **kwargs):

    try:
        super(PlacementWsgify, self).call_func(req, *args, **kwargs)
    except webob.exc.HTTPException as exc:
        LOG.debug('Placement    API    returning    an    error    response:    %s', exc)
        exc.json_formatter = util.json_error_formatter
        raise
