The :func:`locale.localeconv` function now sets temporarily the ``LC_CTYPE``
locale to the ``LC_NUMERIC`` locale to decode ``decimal_point`` and
``thousands_sep`` byte strings if they are non-ASCII or longer than 1 byte, and
the ``LC_NUMERIC`` locale is different than the ``LC_CTYPE`` locale.  This
temporary change affects other threads.

Same change for the :meth:`str.format` method when formatting a number
(:class:`int`, :class:`float`, :class:`float` and subclasses) with the ``n``
type (ex: ``'{:n}'.format(1234)``).