Additional environments where the system misreports the encoding to use (courtesy of Armin Ronacher & Graham Dumpleton on Twitter): upstart, Salt, mod_wsgi.

Note that for more complex applications (e.g. integrated web UIs, socket servers, sending email), round tripping to the standard streams won't be enough - what we really need is a better "source of truth" as to the real system encoding when POSIX compliant systems provide incorrect configuration data to the interpreter.