[errors] Greatly simplify common/errors package.

logdog/server/service/config/poller.go

 // Copyright 2016 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 config
 
 import (
         "time"
 
         "github.com/luci/luci-go/common/clock"
@@ skipping 74 matching lines @@
                                 "currentHash": lastHash,
                         }.Debugf(c, "Content hash matches.")
                 }
         }
 }
 
 // Refresh reloads the configuration value, updating ContentHash.
 func (p *ChangePoller) Refresh(c context.Context) error {
         var meta cfgclient.Meta
         if err := cfgclient.Get(c, cfgclient.AsService, p.ConfigSet, p.Path, nil, &meta); err != nil {
-                return errors.Annotate(err).Reason("failed to reload config %(configSet)s :: %(path)s").
-                        D("configSet", p.ConfigSet).
-                        D("path", p.Path).
-                        Err()
+                return errors.Annotate(err, "failed to reload config %s :: %s", p.ConfigSet, p.Path).Err()
         }
 
         p.ContentHash = meta.ContentHash
         return nil
 }