I recently just got back into screeps, so I decided that I wanted to start from scratch and make my scripts again. While I was doing this I noticed that I kept getting the error message "Script execution has been terminated: CPU bucket is empty". However whenever I look my scripts never go above 2-4 CPU usage. Then I decided that maybe one of my modules was being weird so I started commenting out code until all that's in my main export is a console.log of the CPU bucket, which counts down from 20, displays the error message and then goes back up to 20.
It's not a huge deal, but I am curious why this happens.