The error option specifies an error handling function to call for
server-level errors. Server-level errors include: spyce.spyceNotFound,
spyce.spyceForbidden, spyce.spyceSyntaxError and
spyce.pythonSyntaxError. The string should be of the format
"module:function", and the module should be on the server path. The function
is invoked as function(server, request, response, error) to
generate the error output. The default is "error:serverHandler". Please look
at the serverHandler function in the error module, if you are considering
writing your own server error handler. File-level (or request-level) errors
are handled using the error module.