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

dm/appengine/mutate/schedule_execution.go

 // Copyright 2015 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 mutate
 
 import (
         "fmt"
 
         ds "github.com/luci/gae/service/datastore"
-        "github.com/luci/luci-go/common/errors"
         "github.com/luci/luci-go/common/logging"
         "github.com/luci/luci-go/common/proto/google"
+        "github.com/luci/luci-go/common/retry/transient"
         dm "github.com/luci/luci-go/dm/api/service/v1"
         "github.com/luci/luci-go/dm/appengine/distributor"
         "github.com/luci/luci-go/dm/appengine/model"
         "github.com/luci/luci-go/tumble"
 
         "golang.org/x/net/context"
 )
 
 // ScheduleExecution is a placeholder mutation that will be an entry into the
 // Distributor scheduling state-machine.
@@ skipping 55 matching lines @@
 
         exAuth := &dm.Execution_Auth{Id: eid, Token: e.Token}
 
         var distTok distributor.Token
         distTok, e.TimeToStop, err = dist.Run(&q.Desc, exAuth, prevResult)
         if e.TimeToStop <= 0 {
                 e.TimeToStop = google.DurationFromProto(q.Desc.Meta.Timeouts.Stop)
         }
         e.DistributorToken = string(distTok)
         if err != nil {
-                if errors.IsTransient(err) {
+                if transient.Tag.In(err) {
                         // tumble will retry us later
                         logging.WithError(err).Errorf(c, "got transient error in ScheduleExecution")
                         return
                 }
                 logging.WithError(err).Errorf(c, "got non-transient error in ScheduleExecution")
                 origErr := err
 
                 // put a and e to the transaction buffer, so that
                 // FinishExecution.RollForward can see them.
                 if err = ds.Put(c, a, e); err != nil {
@@ skipping 14 matching lines @@
         if err = ds.Put(c, a, e); err != nil {
                 logging.WithError(err).Errorf(c, "putting attempt+execution")
         }
 
         return
 }
 
 func init() {
         tumble.Register((*ScheduleExecution)(nil))
 }