all: use errgo instead of fmt.Errorf

environs/tools/simplestreams.go

 // Copyright 2013 Canonical Ltd.
 // Licensed under the AGPLv3, see LICENCE file for details.
 
 // The tools package supports locating, parsing, and filtering Ubuntu tools metadata in simplestreams format.
 // See http://launchpad.net/simplestreams and in particular the doc/README file in that project for more information
 // about the file formats.
 package tools
 
 import (
         "bytes"
         "crypto/sha256"
         "fmt"
         "hash"
         "io"
         "path"
         "strings"
         "time"
 
+        errgo "github.com/juju/errgo/errors"
+
         "launchpad.net/juju-core/environs/simplestreams"
         "launchpad.net/juju-core/environs/storage"
         "launchpad.net/juju-core/errors"
         coretools "launchpad.net/juju-core/tools"
         "launchpad.net/juju-core/utils/set"
         "launchpad.net/juju-core/version"
 )
 
 func init() {
         simplestreams.RegisterStructTags(ToolsMetadata{})
@@ skipping 254 matching lines @@
         for _, tm := range tmlist1 {
                 merged[tm.binary()] = tm
         }
         for _, tm := range tmlist2 {
                 binary := tm.binary()
                 if existing, ok := merged[binary]; ok {
                         if tm.Size != 0 {
                                 if existing.Size == 0 {
                                         merged[binary] = tm
                                 } else if existing.Size != tm.Size || existing.SHA256 != tm.SHA256 {
-                                        return nil, fmt.Errorf(
+                                        return nil, errgo.Newf(
                                                 "metadata mismatch for %s: sizes=(%v,%v) sha256=(%v,%v)",
                                                 binary.String(),
                                                 existing.Size, tm.Size,
                                                 existing.SHA256, tm.SHA256,
                                         )
                                 }
                         }
                 } else {
                         merged[binary] = tm
                 }
@@ skipping 86 matching lines @@
 func fetchToolsHash(stor storage.StorageReader, ver version.Binary) (size int64, sha256hash hash.Hash, err error) {
         r, err := storage.Get(stor, StorageName(ver))
         if err != nil {
                 return 0, nil, err
         }
         defer r.Close()
         sha256hash = sha256.New()
         size, err = io.Copy(sha256hash, r)
         return size, sha256hash, err
 }