protected function get_custom_vendor_folder() {
		$maybe_composer_json = WP_CLI_ROOT . '/../../../composer.json';
		if ( ! is_readable( $maybe_composer_json ) ) {
			return false;
		}

		$composer = json_decode( file_get_contents( $maybe_composer_json ) );

		if ( ! empty( $composer->config )
			&& ! empty( $composer->config->{'vendor-dir'} )
		) {
			return $composer->config->{'vendor-dir'};
		}

		return false;
	}