Command for showing upgrades ready to be applied.

def pending():
    """Command for showing upgrades ready to be applied."""
    upgrader = InvenioUpgrader()
    logger = upgrader.get_logger()

    try:
        upgrades = upgrader.get_upgrades()

        if not upgrades:
            logger.info("All upgrades have been applied.")
            return

        logger.info("Following upgrade(s) are ready to be applied:")

        for u in upgrades:
            logger.info(
                " * {0} {1}".format(u.name, u.info))
    except RuntimeError as e:
        for msg in e.args:
            logger.error(unicode(msg))
        raise