A major, breaking issue[1] was how Python 3 handled missing LC_* variables. By default, a Python script would simply crash with any non-ASCII input or output. I

A major, breaking issue[1] was how Python 3 handled missing LC_* variables. By default, a Python script would simply crash with any non-ASCII input or output. It was fixed[2] in 3.5[3]. [1]: https://bugs.python.org/issue19977 https://bugs.python.org/issue19977 [2]: https://www.python.org/dev/peps/pep-0540/ https://www.python.org/dev/peps/pep-0540/ [3]: https://docs.python.org/release/3.5.0/whatsnew/3.5.html https://docs.python.org/release/3.5.0/whatsnew/3.5.html