[macOS] locale.getdefaultlocale() fails with default language set to English

nxdrive/engine/tracker.py:46: in __init__
    self._tracker.set("language", self.current_locale)
nxdrive/engine/tracker.py:69: in current_locale
    encoding = locale.getdefaultlocale()[1] or ""
../deploy-dir/.pyenv/versions/3.7.3/lib/python3.7/locale.py:568: in getdefaultlocale
    return _parse_localename(localename)

localename = 'UTF-8'
    def _parse_localename(localename):
        """ Parses the locale code for localename and returns the
            result as tuple (language code, encoding).
            The localename is normalized and passed through the locale
            alias engine. A ValueError is raised in case the locale name
            cannot be parsed.
            The language code corresponds to RFC 1766.  code and encoding
            can be None in case the values cannot be determined or are
            unknown to this implementation.
        """
        code = normalize(localename)
        if '@' in code:
            # Deal with locale modifiers
            code, modifier = code.split('@', 1)
            if modifier == 'euro' and '.' not in code:
                # Assume Latin-9 for @euro locales. This is bogus,
                # since some systems may use other encodings for these
                # locales. Also, we ignore other modifiers.
                return code, 'iso-8859-15'
        if '.' in code:
            return tuple(code.split('.')[:2])
        elif code == 'C':
            return None, None
>       raise ValueError('unknown locale: %s' % localename)
E       ValueError: unknown locale: UTF-8