'Parses the cron.yaml file.
Args:
basepath: the directory of the application.
appyaml: The app.yaml, if present.
Returns:
A CronInfoExternal object or None if the file does not exist.'

def _ParseCronYaml(self, basepath, appyaml=None):

    cron_yaml = self._ParseYamlFile(basepath, 'cron', croninfo.LoadSingleCron)
    if (not cron_yaml):
        return None
    self._SetApplication(cron_yaml, 'cron', appyaml)
    return cron_yaml
