Comment 1 for bug 1468974

This does indeed seem to be due to subprocess.check_output vs. subprocess.check_call in line 289 of mojo/phase.py. I'd imagine the best solution for this is to add an "interactive" option to the script phase, and if that's passed, to use subprocess.check_call rather than subprocess.check_output. This would mean you'd lose the ability to log the output, but since you're asking for it to happen interactively that may be okay. There may be some more complicated things we can do with subprocesses to display the prompt but still log everything, but depending on how much of a blocker this is that would be the quickest approach.