'Returns a path where we need more disk space, None if all is ok.'

def need_more_disk_space(self, required=0, nodefault=False, ratio=1.0):

    if (not (nodefault and required)):
        required = (ratio * max(required, ((self.sys.minfree_mb * 1024) * 1024)))
    for path in (self.workdir,):
        if (get_free_disk_bytes(path) < required):
            return path
    return None
