Making an explicit note of this so I remember to mention it in the draft PEP: one of the biggest problems that arises in any attempt at a Python-only solution to overriding the locale is that we can end up disagreeing with C/C++ extensions, and this is *especially* a problem when sharing a process with GUI frameworks like Tcl/Tk, Qt, and GTK (since they tend to read the process-wide settings, rather than querying anything that CPython configures during normal operation).

So the approach I'm proposing is to implement a C->C.UTF-8 locale override in the *actual python CLI executable*, and then in the dynamically linked library we only emit a warning if we detect the C locale, we don't actually do anything to change it.