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

common/auth/internal/common.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 internal contains code used internally by common/auth.
 package internal
 
 import (
         "bytes"
         "reflect"
         "strings"
         "sync"
         "time"
 
         "golang.org/x/net/context"
         "golang.org/x/oauth2"
 
         "github.com/luci/luci-go/common/clock"
         "github.com/luci/luci-go/common/data/rand/mathrand"
         "github.com/luci/luci-go/common/errors"
+        "github.com/luci/luci-go/common/retry/transient"
 )
 
 // expiryRandInterval is used by TokenExpiresInRnd.
 const expiryRandInterval = 30 * time.Second
 
 var (
         // ErrInsufficientAccess is returned by MintToken() if token can't be minted
         // for given OAuth scopes. For example, if GCE instance wasn't granted access
         // to requested scopes when it was created.
         ErrInsufficientAccess = errors.New("can't get access token for given scopes")
@@ skipping 218 matching lines @@
                 return nil, err
         case isBadKeyError(err):
                 return nil, err
         case err != nil:
                 // More often than not errors here are transient (network connectivity
                 // errors, HTTP 500 responses, etc). It is difficult to categorize them,
                 // since oauth2 library uses fmt.Errorf(...) for errors. Retrying a fatal
                 // error a bunch of times is not very bad, so pick safer approach and assume
                 // any error is transient. Revoked refresh token or bad credentials (most
                 // common source of fatal errors) is already handled above.
-                return nil, errors.WrapTransient(err)
+                return nil, transient.Tag.Apply(err)
         default:
                 return tok, nil
         }
 }