Incorrect detection of utf-8-sig encoding

[livercat]

Test data:
data = "some text".encode('utf-8-sig')

Detection result:
cchardet 1.1.3: {'encoding': 'UTF-8', 'confidence': 0.9900000095367432}
cchardet 2.0.0: {'encoding': 'UTF-8', 'confidence': 0.9900000095367432}
chardet 3.0.2: {'encoding': 'UTF-8-SIG', 'confidence': 1.0, 'language': ''}