FIX: Do not return priority fortified systems.

    deferred, priority = [], []

    for system in fort_get_systems(session):

        if system.is_fortified:

            continue

        if 'priority' in system.notes.lower():

            priority += [system]

        elif system.missing < DEFER_MISSING and not system.is_fortified:

        elif system.missing < DEFER_MISSING:

            deferred += [system]

    return priority, deferred