memcache/memcache.go
func singleError(err error) error {
	if me, ok := err.(appengine.MultiError); ok {
		return me[0]
	}
	return err
}
func singleError(err error) error {
	if me, ok := err.(appengine.MultiError); ok {
		return me[0]
	}
	return err
}
// If err is an appengine.MultiError, return its first element. Otherwise, return err.