[errors] Greatly simplify common/errors package.

logdog/client/butler/streamserver/tcp.go

 // Copyright 2017 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 streamserver
 
 import (
         "fmt"
         "net"
 
@@ skipping 39 matching lines @@
 // exported stream server parameters (externally) or by calling Address
 // (internally).
 func NewTCP6Server(ctx context.Context, spec string) (StreamServer, error) {
         return newTCPServerImpl(ctx, "tcp6", spec, net.IPv6loopback)
 }
 
 // Listen implements StreamServer.
 func newTCPServerImpl(ctx context.Context, netType, spec string, loopback net.IP) (StreamServer, error) {
         tcpAddr, err := net.ResolveTCPAddr(netType, spec)
         if err != nil {
-                return nil, errors.Annotate(err).Reason("could not resolve %(net)q address %(addr)q").
-                        D("net", netType).
-                        D("addr", spec).
-                        Err()
+                return nil, errors.Annotate(err, "could not resolve %q address %q", netType, spec).Err()
         }
 
         if tcpAddr.IP == nil {
                 tcpAddr.IP = loopback
         }
 
         return &listenerStreamServer{
                 Context: ctx,
                 address: fmt.Sprintf("%s:%s", netType, tcpAddr.String()),
                 gen: func() (net.Listener, string, error) {
                         l, err := net.ListenTCP(netType, tcpAddr)
                         if err != nil {
-                                return nil, "", errors.Annotate(err).Reason("failed to listen to %(net)q address %(addr)q").
-                                        D("net", netType).
-                                        D("addr", tcpAddr).
-                                        Err()
+                                return nil, "", errors.Annotate(err, "failed to listen to %q address %q", netType, tcpAddr).Err()
                         }
 
                         addr := fmt.Sprintf("%s:%s", netType, l.Addr().String())
                         log.Fields{
                                 "addr": addr,
                         }.Debugf(ctx, "Listening on %q stream server...", netType)
                         return l, addr, nil
                 },
         }, nil
 }