improve IAM module

Signed-off-by: hongming <talonwan@yunify.com>

vendor/go.etcd.io/etcd/clientv3/balancer/picker/err.go

@@ -0,0 +1,39 @@
+// Copyright 2018 The etcd Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package picker
+
+import (
+	"context"
+
+	"google.golang.org/grpc/balancer"
+)
+
+// NewErr returns a picker that always returns err on "Pick".
+func NewErr(err error) Picker {
+	return &errPicker{p: Error, err: err}
+}
+
+type errPicker struct {
+	p   Policy
+	err error
+}
+
+func (ep *errPicker) String() string {
+	return ep.p.String()
+}
+
+func (ep *errPicker) Pick(context.Context, balancer.PickOptions) (balancer.SubConn, func(balancer.DoneInfo), error) {
+	return nil, nil, ep.err
+}