autoflake.py
def detect_encoding(filename, limit_byte_check=-1):
    """Return file encoding."""
    try:
        with open(filename, 'rb') as input_file:
            encoding = _detect_encoding(input_file.readline)

            # Check for correctness of encoding.
            with open_with_encoding(filename, encoding) as input_file:
                input_file.read(limit_byte_check)

        return encoding
    except (LookupError, SyntaxError, UnicodeDecodeError):
        return 'latin-1'
def detect_encoding(filename, limit_byte_check=-1):
    """Return file encoding."""
    try:
        with open(filename, 'rb') as input_file:
            encoding = _detect_encoding(input_file.readline)

            # Check for correctness of encoding.
            with open_with_encoding(filename, encoding) as input_file:
                input_file.read(limit_byte_check)

        return encoding
    except (LookupError, SyntaxError, UnicodeDecodeError):
        return 'latin-1'
Return file encoding.