I am a beginner when it comes to open source contribution and have decided to take up this issue. I did some basic research about the issue found this file: cpython/Lib/test/support/script_helper.py The function _assert_python call run_python_until_end which call subprocess.Popen which takes the parameter universal_newlines=True. But I think that I don't understand this issue. Could anyone guide me from this point forward? Regards, Pranav