How to skip 'Please remove the installation medium then press enter'

I have a time-consuming program running in Lubuntu 18.04 Live. It will take around one day to finish. After the program finishes the computer shuts down. But since I am running Lubuntu Live, the computer asks me to > Please remove the installation medium then press enter after initiating the shutdown. I will be traveling away before the program can finish and will not be back in a few weeks. I don't want the computer to be powered on all that time. My question is: Is there a timeout after which the computer will eventually shut down, or is there any way to skip this prompt and completely shut down Lubuntu Live?