[errors] de-specialize Transient in favor of Tags.

tokenserver/appengine/impl/utils/revocation/id.go

 // Copyright 2017 The LUCI Authors. All rights reserved.
 // Use of this source code is governed under the Apache License, Version 2.0
 // that can be found in the LICENSE file.
 
 package revocation
 
 import (
         "golang.org/x/net/context"
 
         "github.com/luci/gae/service/datastore"
-        "github.com/luci/luci-go/common/errors"
+        "github.com/luci/luci-go/common/retry/transient"
 )
 
 // GenerateTokenID produces an int64 that can be used as a token identifier.
 //
 // We reuse datastore ID generator to produce token ids. The tokens are not
 // actually stored in the datastore. The generated ID sequence is associated
 // with some entity kind (indicated via 'kind'). If we ever need to restart the
 // ID sequence, this kind can be changed.
 func GenerateTokenID(c context.Context, kind string) (int64, error) {
         // Note: AllocateIDs modifies passed slice in place, by replacing the keys
         // there.
         keys := []*datastore.Key{
                 datastore.NewKey(c, kind, "", 0, nil),
         }
         if err := datastore.AllocateIDs(c, keys); err != nil {
-                return 0, errors.WrapTransient(err)
+                return 0, transient.Tag.Apply(err)
         }
         return keys[0].IntID(), nil
 }