public function startElement($tag, $attrs)
    {
        if ($tag === "project") {
            $ph = new ProjectHandler($this->parser, $this, $this->configurator, $this->context);
            $ph->init($tag, $attrs);
        } else {
            throw new ExpatParseException(
                "Unexpected tag <$tag> in top-level of build file.",
                $this->parser->getLocation()
            );
        }
    }