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

server/auth/internal/fetch.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
 
 import (
         "bytes"
         "encoding/json"
         "fmt"
         "io/ioutil"
         "net/http"
 
-        "github.com/luci/luci-go/common/errors"
         "github.com/luci/luci-go/common/logging"
+        "github.com/luci/luci-go/common/retry/transient"
 
         "golang.org/x/net/context"
         "golang.org/x/net/context/ctxhttp"
 )
 
 // ClientFactory knows how to produce http.Client that attach proper OAuth
 // headers.
 //
 // If 'scopes' is empty, the factory should return a client that makes anonymous
 // requests.
@@ skipping 85 matching lines @@
 func fetchJSON(c context.Context, client *http.Client, val interface{}, f func() (*http.Request, error)) error {
         r, err := f()
         if err != nil {
                 logging.Errorf(c, "auth: URL fetch failed - %s", err)
                 return err
         }
         logging.Infof(c, "auth: %s %s", r.Method, r.URL)
         resp, err := ctxhttp.Do(c, client, r)
         if err != nil {
                 logging.Errorf(c, "auth: URL fetch failed, can't connect - %s", err)
-                return errors.WrapTransient(err)
+                return transient.Tag.Apply(err)
         }
         defer func() {
                 ioutil.ReadAll(resp.Body)
                 resp.Body.Close()
         }()
         if resp.StatusCode >= 300 {
                 body, _ := ioutil.ReadAll(resp.Body)
                 // Opportunistically try to unmarshal the response. Works with JSON APIs.
                 if val != nil {
                         json.Unmarshal(body, val)
                 }
                 logging.Errorf(c, "auth: URL fetch failed - HTTP %d - %s", resp.StatusCode, string(body))
                 err := fmt.Errorf("auth: HTTP code (%d) when fetching %s", resp.StatusCode, r.URL)
                 if resp.StatusCode >= 500 {
-                        return errors.WrapTransient(err)
+                        return transient.Tag.Apply(err)
                 }
                 return err
         }
         if val != nil {
                 if err = json.NewDecoder(resp.Body).Decode(val); err != nil {
                         logging.Errorf(c, "auth: URL fetch failed, bad JSON - %s", err)
                         return fmt.Errorf("auth: can't deserialize JSON at %q - %s", r.URL, err)
                 }
         }
         return nil
 }