We should first implement the same algorithm of the 3 normalization functions and add tests for them (at least for the function in normalization):
- normalize_encoding() in encodings: it doesn't convert to lowercase and keep non-ASCII letters
- normalize_encoding() in unicodeobject.c
- normalizestring() in codecs.c
normalize_encoding() in encodings is more laxist than the two other functions: it normalizes " utf 8 " to 'utf_8'. But it doesn't convert to lowercase and keeps non-ASCII letters: "UTF-8é" is normalized "UTF_8é".
I don't know if the normalization functions have to be more or less strict, but I think that they should all give the same result.