public function readPoFile(string $file, ?resource $context = null): void
    {
        $oldEr = error_reporting(E_ALL ^ E_WARNING);
        $source = file_get_contents($file, false, $context);
        error_reporting($oldEr);
        if (false===$source) {
            throw new FileNotReadableException($file);
        }
        $this->parsePoSource($source);
    }