[errors] Greatly simplify common/errors package.

logdog/client/butlerlib/streamclient/tcp.go

Index: logdog/client/butlerlib/streamclient/tcp.go
diff --git a/logdog/client/butlerlib/streamclient/tcp.go b/logdog/client/butlerlib/streamclient/tcp.go
index 058be4851f15e831835139f81830dbfcef515ac8..16ee4075d2a103a8ee9b413d1494b04e4df04963 100644
--- a/logdog/client/butlerlib/streamclient/tcp.go
+++ b/logdog/client/butlerlib/streamclient/tcp.go
@@ -15,16 +15,11 @@ func tcpProtocolClientFactory(netType string) ClientFactory {
 	return func(spec string) (Client, error) {
 		raddr, err := net.ResolveTCPAddr(netType, spec)
 		if err != nil {
-			return nil, errors.Annotate(err).Reason("could not resolve %(net)q address from %(spec)q").
-				D("net", netType).
-				D("spec", spec).
-				Err()
+			return nil, errors.Annotate(err, "could not resolve %q address from %q", netType, spec).Err()
 		}
 
 		if raddr.IP == nil || raddr.IP.IsUnspecified() {
-			return nil, errors.Reason("a valid %(net)q address must be provided").
-				D("net", netType).
-				Err()
+			return nil, errors.Reason("a valid %q address must be provided", netType).Err()
 		}
 
 		if raddr.Port <= 0 {
@@ -35,10 +30,7 @@ func tcpProtocolClientFactory(netType string) ClientFactory {
 			factory: func() (io.WriteCloser, error) {
 				conn, err := net.DialTCP(netType, nil, raddr)
 				if err != nil {
-					return nil, errors.Annotate(err).Reason("failed to dial %(net)q address %(raddr)q").
-						D("net", netType).
-						D("raddr", raddr).
-						Err()
+					return nil, errors.Annotate(err, "failed to dial %q address %q", netType, raddr).Err()
 				}
 				return conn, nil
 			},