code: static function checkArg($argName, $value)
      {
          Checker::argStringNonEmpty($argName, $value);
  
          $error = self::findError($value);
          if ($error !== null) throw new \InvalidArgumentException("'$argName': bad path: $error: ".Util::q($value));
      }
docs: @internal
  
  @param string $argName
  @param mixed $value
  @throws \InvalidArgumentException