PrinterJob.getPrintService() will always return null in the sandbox
This is because in UnixPrintServiceLookup.java, method execCmd, it tries
to execute lpstat to find out the available print service on the system,
and redirects the lpstat output to a temp file created with
But File.createTempFile will fail in the sandbox because we don't have
permissions to create file on the local system. So all the lookup on
print service will return null.