In GetApplicationToken.py the app_scope too is too broad.

[matecsaj]

app_scopes = ["https://api.ebay.com/oauth/api_scope", "https://api.ebay.com/oauth/api_scope/buy.item.feed"]

should be

app_scopes = ["https://api.ebay.com/oauth/api_scope"]

or this will occur

Error: invalid_scope - The requested scope is invalid, unknown, malformed, or exceeds the scope granted to the client

Perhaps, accounts granted extra privileges can get away with it, but a basic account can't.