Hello there,

It seems like the base_url passed to the default constructor is not used to fetch the access token for app authentication.

Here's an example code:

app_id = "XXX"
app_private_key = "XXX"
installation_id = "XXX"
g = github.Github(
    base_url="https://custom-github-url.com"
    app_auth=github.AppAuthentication(
        app_id=app_id,
        private_key=app_private_key,
        installation_id=installation_id,
    ),
)

Whatever base_url is passed, the following error occurs:
requests.exceptions.ConnectionError: HTTPSConnectionPool(host='api.github.com', port=443): Max retries exceeded with url: XXX

As can be seen in the stack trace, the host is the one defined here, which is DEFAULT_BASE_URL = "https://api.github.com".

I suspect the error comes from here. The param base_url is not passed to GithubIntegration which therefore uses the default url.