With PEPs 538 and 540 merged for Python 3.7 (so we'll almost always use UTF-8 instead of ASCII when the platform nominates the C or POSIX locale as the currently active one), and Windows previously switching to assuming UTF-8 instead of mbcs for binary interfaces in Python 3.6, I think this tracking issue has served its purpose.

Of the issues previously mentioned here, the following are still open:

* Improved Unicode handling in the Windows console: issue 17620
* Utilities for clearing out surrogates from strings: issue 18814
* Treating "wsgistr" as a serialisation format: issue 22264
* Defining a formatting mini-language for hex output: issue 22385

I don't think any of those share enough characteristics to be worth continuing to track as a group, so I'm closing this meta-issue as out of date :)