Return a list of the new modules, pass an lsmod dict before running
    modprobe and one after modprobe has run

def _rm_mods(pre_mods, post_mods):
    '''
    Return a list of the new modules, pass an lsmod dict before running
    modprobe and one after modprobe has run
    '''
    pre = set()
    post = set()
    for mod in pre_mods:
        pre.add(mod['module'])
    for mod in post_mods:
        post.add(mod['module'])
    return pre - post