Inconsistent character encoding from windows output

Looking at this issue in the JupyterLab repo, we wanted to migrate it here since it's not related to the JupyterLab frontend: https://github.com/jupyterlab/jupyterlab/issues/1239

Original report:

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trying "!dir" in Jupyterlab Notebook, hoping for the best as there may be some "utf-8" standardization thanks to PEP 528 / 529, I see no effect: still badly decoded characters.

I have difficulties to guess from bugs.python.org if something can be done in Jupyterlab (or qtconsole) case: https://bugs.python.org/issue28675

Maybe I don't take the right example to see the PEP 528 / 529 effects.