Run with Python UTF-8 mode enabled?

There's [a proposal](https://discuss.python.org/t/pep-597-enable-utf-8-mode-by-default-on-windows/3122) for Python to use UTF-8 mode on Windows by default. Most significantly, this means that `open()`-ing a file in text mode would use UTF-8 by default rather than a locale-dependent encoding.

This is controversial, and one step that has been suggested is for Jupyter to enable UTF-8 mode for kernels before a change is made in Python, to explore how well it works. Changing the default is arguably also more favourable to new programmers who don't have a lot of existing code, and Jupyter is often used in teaching settings.

I'm strongly in favour of changing the default in Python, but I'd be -0.5 on only changing it in Jupyter, because that would mean code inside Jupyter behaves differently from code outside. But I'd be more in favour if changing it in Jupyter was a prelude to, or test case for, changing it in Python.