Oh, PYTHONCOERCECLOCALE env var is read very early in main() by _Py_CoerceLegacyLocale(), it ignores -E command line option.

     * Ignoring -E and -I is safe from a security perspective, as we only use
     * the setting to turn *off* the implicit locale coercion, and anyone with
     * access to the process environment already has the ability to set
     * `LC_ALL=C` to override the C level locale settings anyway.