'Load a grading policy from the specified paths, in order, if it exists.'

@classmethod
def read_grading_policy(cls, paths, system):

    policy_str = '{}'
    for policy_path in paths:
        if (not system.resources_fs.exists(policy_path)):
            continue
        log.debug('Loading    grading    policy    from    {0}'.format(policy_path))
        try:
            with system.resources_fs.open(policy_path) as grading_policy_file:
                policy_str = grading_policy_file.read()
                break
        except IOError:
            msg = "Unable    to    load    course    settings    file    from    '{0}'".format(policy_path)
            log.warning(msg)
    return policy_str
