def copy_attr(f1, f2):
    """ copies the special packaging file attributes from f1 to f2.
    """
    copyit = lambda x: not hasattr(f2, x) and x[:10] == 'PACKAGING_'
    if f1._tags:
        pattrs = [tag for tag in f1._tags if copyit(tag)]
        for attr in pattrs:
            f2.Tag(attr, f1.GetTag(attr))
copies the special packaging file attributes from f1 to f2.