private function boot() {
		list( $locations, $config ) = $this->get_engine_config();

		$loader = new Twig_Loader_Filesystem( $locations );
		$env    = new Twig_Environment( $loader, $config );

		if ( defined( 'WP_DEBUG' ) && WP_DEBUG ) {
			$env->addExtension( new Twig_Extension_Debug() );
		}

		return $env;
	}