ippd: use super() to get next MRO class's method.
ippd: use %r to substitute value of repr().
ippd: no need to be explicit about default here.
ippd: JobAddress fix.
ippd: IPPServer.send_ipp_error() is now IPPServer.send_ipp_statuscode().

It can now be used to send 'success' responses, as well as providing a
status-message.