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

tokenserver/appengine/impl/utils/policy/entities.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 policy
 
 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"
 )
 
 // importedPolicyHeader is an entity that holds metadata about a cached policy.
 //
 // Most crucially, it stores a digest of serialized policy configs. It is used
 // by Policy.Queryable() to quickly detect that no changes to the config have
 // been made.
 //
 // The actual serialized configs (that are much heavier than metadata) are
 // stored in a separate child entity, fetched only when they are really needed.
@@ skipping 26 matching lines @@
                 Name:     name,
                 Revision: rev,
                 SHA256:   sha256,
         }
         body := &importedPolicyBody{
                 Parent:   datastore.KeyForObj(c, header),
                 Revision: rev,
                 SHA256:   sha256,
                 Data:     serialized,
         }
-        return errors.WrapTransient(datastore.RunInTransaction(c, func(c context.Context) error {
+        return transient.Tag.Apply(datastore.RunInTransaction(c, func(c context.Context) error {
                 return datastore.Put(c, header, body)
         }, nil))
 }
 
 // getImportedPolicyHeader loads importedPolicyHeader entity from the datastore.
 //
 // Returns (nil, nil) if there's no such entity.
 func getImportedPolicyHeader(c context.Context, name string) (*importedPolicyHeader, error) {
         e := &importedPolicyHeader{Name: name}
         switch err := datastore.Get(c, e); {
         case err == datastore.ErrNoSuchEntity:
                 return nil, nil
         case err != nil:
-                return nil, errors.WrapTransient(err)
+                return nil, transient.Tag.Apply(err)
         }
         return e, nil
 }
 
 // getImportedPolicyBody loads importedPolicyBody entity from the datastore.
 //
 // Returns (nil, nil) if there's no such entity.
 func getImportedPolicyBody(c context.Context, name string) (*importedPolicyBody, error) {
         e := &importedPolicyBody{
                 Parent: datastore.KeyForObj(c, &importedPolicyHeader{Name: name}),
         }
         switch err := datastore.Get(c, e); {
         case err == datastore.ErrNoSuchEntity:
                 return nil, nil
         case err != nil:
-                return nil, errors.WrapTransient(err)
+                return nil, transient.Tag.Apply(err)
         }
         return e, nil
 }