def _build_locale_table(filename_or_file):
    """
    Parses the FacebookLocales.xml file and builds a dict relating every
    available language ('en, 'es, 'zh', ...) with a list of available regions
    for that language ('en' -> 'US', 'EN') and an (arbitrary) default region.
    """
    # Require the XML parser module only if we want the default mapping
    from xml.dom.minidom import parse

    dom = parse(filename_or_file)

    reps = dom.getElementsByTagName('representation')
    locs = map(lambda r: r.childNodes[0].data, reps)

    locale_map = {}
    for loc in locs:
        lang, _, reg = loc.partition('_')
        lang_map = locale_map.setdefault(lang, {'regs': [], 'default': reg})
        lang_map['regs'].append(reg)

    # Default region overrides (arbitrary)
    locale_map['en']['default'] = 'US'
    # Special case: Use es_ES for Spain and es_LA for everything else
    locale_map['es']['default'] = 'LA'
    locale_map['zh']['default'] = 'CN'
    locale_map['fr']['default'] = 'FR'
    locale_map['pt']['default'] = 'PT'

    return locale_map