Fixed version of IPyton.completer.completions_sorting_key

def completions_sorting_key(cls, word):
        "Fixed version of IPyton.completer.completions_sorting_key"
        prio1, prio2 = 0, 0
        if word.startswith('__'):  prio1 = 2
        elif word.startswith('_'): prio1 = 1
        if word.endswith('='):     prio1 = -1
        if word.startswith('%%'):
            if not "%" in word[2:]:
                word = word[2:];   prio2 = 2
        elif word.startswith('%'):
            if not "%" in word[1:]:
                word = word[1:];   prio2 = 1
        return prio1, word, prio2