def on_error(self, ex):
        if self._d:
            self._d.errback()
            self._d = None
Extract the identity from the Keystone auth component.
dataset/ETHPy150Open couchbase/couchbase-python-client/txcouchbase/bucket.py/BatchedRowMixin.on_error--crossover with--dataset/ETHPy150Open openstack/swift/swift/common/middleware/keystoneauth.py/KeystoneAuth._keystone_identity