Another thought: you probably don't need to capture the output from the subprocess runs, then print it. I think you should be able to just remove the output-capturing and let the subprocess print it directly?
However, if you ever want to switch to a combinator template grader, you not only need to capture all the output, you need to package it all up into the JSON result that should be the only output from the run.
However, if you ever want to switch to a combinator template grader, you not only need to capture all the output, you need to package it all up into the JSON result that should be the only output from the run.