Validate JSON file

[snippsat]

invalid json: 'charmap' codec can't decode byte 0x81 in position 145717: character maps to <undefined>

I also discovered that if I enter (python -m json.tool "C:\Engineering\test2\assetLink_tr-TR.json") on the CMD line, it works as what I am looking for. But I would still like to find out why the script does not work on UTF-8 JSON files.

Remember on Widows should and most in many cases most specify which encoding that should be used.
If not it will use charmap codec.

with open(fname, encoding='utf-8') as f:

The default encoding for Python 3 source code is utf-8,but read in and out OS may mess that up.
So as example both read and write do specify what encoding to use,
and that's always utf-8 if code starts in Python or as a first try in almost all cases.

s = 'Crème and Spicy jalapeño ☂'
with open('unicode.txt', 'w', encoding='utf-8') as f_out:
    f_out.write(s)

with open('unicode.txt', encoding='utf-8') as f:
    print(f.read())

Output:
Crème and Spicy jalapeño ☂