GrumPHP\Linter\Xml\XmlLinter::locateScheme PHP Method

    private function locateScheme(SplFileInfo $xmlFile, $scheme)
    {
        if (filter_var($scheme, FILTER_VALIDATE_URL)) {
            return $this->loadFromNet ? $scheme : null;
        }
        $schemeFile = new SplFileInfo($xmlFile->getPath() . DIRECTORY_SEPARATOR . $scheme);
        return $schemeFile->isReadable() ? $schemeFile->getPathname() : null;
    }