want   bool
	}{
		{
			name:   "url.Error",
			err:    &url.Error{Op: "PUT", URL: "http://localhost/1234", Err: restError("remote server offline")},
			target: &url.Error{},
			want:   true,
		},
		{
			name: "net.Error",
			err:  &url.Error{Op: "PUT", URL: "http://localhost/1234", Err: restError("remote server offline")},
			want: true,
		},
		{
			name: "net.Error-unmatched",
			err:  errors.New("something"),

	newAuthToken func(audience string) string

	sync.RWMutex // mutex for lastErr
	lastErr      error
	lastErrTime  time.Time
}

type restError string

func (e restError) Error() string {
	return string(e)
}

func (e restError) Timeout() bool {
	return true
}

// Given a string of the form "host", "host:port", or "[ipv6::address]:port",
// return true if the string includes a port.