UnicodeDecodeError: 'ascii' codec can't decode

[ddtmax]

[Info] Install/Update service client_secrets file
[Info] Start WebUI for handling oauth2
Traceback (most recent call last):
File "/hassio_oauth.py", line 76, in
user_data = json.load(data)['installed']
File "/usr/lib/python3.5/json/init.py", line 265, in load
return loads(fp.read(),
File "/usr/lib/python3.5/encodings/ascii.py", line 26, in decode
return codecs.ascii_decode(input, self.errors)[0]
UnicodeDecodeError: 'ascii' codec can't decode byte 0xff in position 12: ordinal not in range(128)