ing and '?' on encoding.
         'surrogateescape' - replace with private code points U+DCnn.
         'xmlcharrefreplace' - Replace with the appropriate XML
                               character reference (only for encoding).
         'backslashreplace'  - Replace with backslashed escape sequences.
         'namereplace'       - Replace with \N{...} escape sequences
                               (only for encoding).

        The set of allowed values can be extended via register_error.

    Ú