holdMessage fails: unknown encoding

[Curtis Hovey]

Mailman sent a message to a lists moderation queue, but it never arrived:

zope.app.publisher.xmlrpc.metaconfigure.MailingListAPIView instance at 0xada9710>
  Module zope.publisher.publish, line 115, in debug_call
    return obj(*args)
  Module canonical.launchpad.xmlrpc.mailinglist, line 254, in holdMessage
    message = getUtility(IMessageSet).fromEmail(bytes)
  Module canonical.launchpad.database.message, line 330, in fromEmail
    subject = self._decode_header(parsed_message.get('subject', ''))
  Module canonical.launchpad.database.message, line 258, in _decode_header
    (bytes.decode(charset, 'replace').encode('utf-8'), 'utf-8'))
LookupError: unknown encoding: windows-874

In the case of holdMessage(), mailman has already determined the message is a problem and is placing a copy of it in a queue for a person to approve or discard. We might be able to force the encoding to ascii, dropping unknown characters.

[Curtis Hovey (sinzui)]

This is a modern form of bug 294353