GitHub Enterprise Server Avatar

It would be nice if the avatars would also work with a GitHub Enterprise server.

I have found the low-level property avatar.serverUrl to fetch the avatars. The GitHub avatar can be fetched via github.com/user_name.png?size=64.
Currently in avatar.serverUrl only the email in md5 is available. In my cause I would need only a part of the email (user_name@email.com) and not in md5.

But also using the GitHub User API should work which returns a JSON containing the avatar URL.