Emitted when processing has failed for a message.
This could mean either that it could not be read (if
SoupServer::request-read has not been emitted for it yet), or that
the response could not be written back (if
has been emitted but
SoupServer::request-finished has not been).
message is in an undefined state when this signal is
emitted; the signal exists primarily to allow the server to
free any state that it may have allocated in
The default handler is called before the handlers added via
The data is owned by the caller of the function.