runbuilds.py is busy printing to the console which , since you also use the console for command line builds, is very messy. Its output should really goto a log file like the toaster_web_ui does.
sent to toaster ml: https://patchwork.openembedded.org/series/5104/
master : 3b7ab16bf8bbfa0e38fa35a31142853eb8d6f760