[errors] Greatly simplify common/errors package.

logdog/appengine/coordinator/service.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 coordinator
 
 import (
         "sync"
         "sync/atomic"
         "time"
@@ skipping 490 matching lines @@
 func (si *googleStorage) Close() {
         if err := si.gs.Close(); err != nil {
                 log.WithError(err).Warningf(si.ctx, "Failed to close Google Storage client.")
         }
         si.Storage.Close()
 }
 
 func (si *googleStorage) GetSignedURLs(c context.Context, req *URLSigningRequest) (*URLSigningResponse, error) {
         info, err := si.svc.signer.ServiceInfo(c)
         if err != nil {
-                return nil, errors.Annotate(err).InternalReason("failed to get service info").Err()
+                return nil, errors.Annotate(err, "").InternalReason("failed to get service info").Err()
         }
 
         lifetime := req.Lifetime
         switch {
         case lifetime < 0:
-                return nil, errors.Reason("invalid signed URL lifetime: %(lifetime)s").D("lifetime", lifetime).Err()
+                return nil, errors.Reason("invalid signed URL lifetime: %s", lifetime).Err()
 
         case lifetime > maxSignedURLLifetime:
                 lifetime = maxSignedURLLifetime
         }
 
         // Get our signing options.
         resp := URLSigningResponse{
                 Expiration: clock.Now(c).Add(lifetime),
         }
         opts := gcst.SignedURLOptions{
                 GoogleAccessID: info.ServiceAccountName,
                 SignBytes: func(b []byte) ([]byte, error) {
                         _, signedBytes, err := si.svc.signer.SignBytes(c, b)
                         return signedBytes, err
                 },
                 Method:  "GET",
                 Expires: resp.Expiration,
         }
 
         doSign := func(path gs.Path) (string, error) {
                 url, err := gcst.SignedURL(path.Bucket(), path.Filename(), &opts)
                 if err != nil {
-                        return "", errors.Annotate(err).InternalReason("failed to sign URL").
-                                D("bucket", path.Bucket()).D("filename", path.Filename).Err()
+                        return "", errors.Annotate(err, "").InternalReason(
+                                "failed to sign URL: bucket(%s)/filename(%s)", path.Bucket(), path.Filename).Err()
                 }
                 return url, nil
         }
 
         // Sign stream URL.
         if req.Stream {
                 if resp.Stream, err = doSign(si.stream); err != nil {
-                        return nil, errors.Annotate(err).InternalReason("failed to sign stream URL").Err()
+                        return nil, errors.Annotate(err, "").InternalReason("failed to sign stream URL").Err()
                 }
         }
 
         // Sign index URL.
         if req.Index {
                 if resp.Index, err = doSign(si.index); err != nil {
-                        return nil, errors.Annotate(err).InternalReason("failed to sign index URL").Err()
+                        return nil, errors.Annotate(err, "").InternalReason("failed to sign index URL").Err()
                 }
         }
 
         return &resp, nil
 }