Authentication Issue: UnicodeDecodeError

[i-bond]

Hello, everyone! I was following the quickstart guide on PyDrive, downloaded client_secret_.json. file, renamed it and encountered the following issue:

from pydrive.auth import GoogleAuth 
gauth = GoogleAuth() 
gauth.LocalWebserverAuth()

UnicodeDecodeError: 'utf-8' codec can't decode byte 0xcf in position 0: invalid continuation byte

Tried to change encoding to latin-1:

import codecs
BLOCKSIZE = 1048576 # or some other, desired size in bytes

with codecs.open(source_path, "r", "utf-8") as sourceFile:
    with codecs.open('client_secrets.json', "w", "latin-1") as targetFile:
        while True:
            contents = sourceFile.read(BLOCKSIZE)
            if not contents:
                break
            targetFile.write(contents)

But after this it throws another error:
JSONDecodeError: Expecting value: line 1 column 1 (char 0)

Could you help me to find out what causes these errors and how to properly authenticate with PyDrive?