task: #3616275 Use the PECL YAML parser for info file parsing when available

    }

    try {

      // If the PECL YAML extension is available, use that to parse .info.yml

      // files. The PECL YAML extension can be as much as five times faster as

      // Symfony's YAML parser, however it does not support the advanced YAML

      // features that we rely on in e.g. the configuration system. We do not

      // need those advanced features in .info.yml files, but they are also

      // parsed very frequently during tests, so in this specific case it's

      // worth using where available and falling back to Symfony's parser

      // otherwise.

      if (extension_loaded('yaml')) {

        // The PECL YAML parser triggers PHP warnings when YAML is invalid. For

        // consistency with the Symfony parser, convert these to exceptions.

        set_error_handler(function ($error_number, $error_string, $error_file, $error_line) {

          throw new \ErrorException($error_string, 0, $error_number, $error_file, $error_line);

        });

        try {

          $parsed_info = yaml_parse(file_get_contents($filename));

        }

        catch (\ErrorException $e) {

          throw new InvalidDataTypeException($e->getMessage());

        }

        finally {

          restore_error_handler();

        }

        if ($parsed_info === FALSE) {

          throw new InvalidDataTypeException();

        }

      }

      else {

        $parsed_info = Yaml::decode(file_get_contents($filename));

      }

    }

    catch (InvalidDataTypeException $e) {

      throw new InfoParserException("Unable to parse $filename " . $e->getMessage());

    }