We currently detect EUC-TW pretty well, but it's not actually supported by Python. Most users would expect that

result = chardet.detect(some_bytes)
try:
    some_bytes.decode(result['encoding'])
except UnicodeDecodeError:
    print('Oops. chardet detected the wrong encoding')

would always work, but the decode line can actually fail with a LookupError too because of encodings that aren't supported by Python.