'Encrypt the new object headers with a new iv and the current crypto.
Note that an object may have encrypted headers while the body may
remain unencrypted.'

def handle_post(self, req, start_response):

    self._check_headers(req)
    keys = self.get_keys(req.environ)
    self.encrypt_user_metadata(req, keys)
    resp = self._app_call(req.environ)
    start_response(self._response_status, self._response_headers, self._response_exc_info)
    return resp
