how to ignore invalid byte sequence for encoding without using sql_ascii?

I am now importing the dump file of wikipedia into my postgresql using
maintains/importDump.php. It fails on 'ERROR: invalid byte sequence
for encoding UTF-8'. Is there any way to let pgsql just ignore the
invalid characters ( i mean that drop the invalid ones ), that the
script will keep going without die on this error.

I know that i can using sql_ascii or even modify the importDump.php,
but those are not so easy to do as i thought.

thanks for help