get_csv function invalid start byte

[ghost]

i use the get_csv function ,in python3.7, but some time will devodeError,
error code on :
https://github.com/guinslym/pyexifinfo/blob/master/pyexifinfo/pyexifinfo.py#L141

I local fix it use this function ,replace s = s.decode('utf-8'), can fix it ,please update

def byte_to_str(byte_str):
if isinstance(byte_str, str):
return byte_str
chard = chardet.detect(byte_str)
if chard.get('encoding'):
byte_str = byte_str.decode(chard['encoding'], 'ignore')
else:
byte_str = byte_str.decode('utf8', 'ignore')
return byte_str

error info:

File "/opt/venv3/lib/python3.7/site-packages/pyexifinfo/pyexifinfo.py", line 143, in get_csv
s = s.decode('utf-8')
UnicodeDecodeError: 'utf-8' codec can't decode byte 0xb9 in position 1313: invalid start byte