'Determine if a response should be decrypted, and if so then fetch keys.
:param req: a Request object
:returns: a dict of decryption keys'

def get_decryption_keys(self, req):

    if config_true_value(req.environ.get('swift.crypto.override')):
        self.logger.debug('No    decryption    is    necessary    because    of    override')
        return None
    return self.get_keys(req.environ)
