Which version of GitPython are you using ? There has been a bug that could cause it to omit certain messages to stderr in the past.

Besides, as a general note, GitPython will do auth only without any user input. Usually this works by supplying a working ssh configuration, or by configuring GIT_SSH_COMMAND via the custom environment functionality of repo.git.

I'm creating a GUI that I hope can make it easier to use GIT.
To that end I do not want to have to require the user to any complex setup and the SSH stufff is
more complex then useing https for example.

I think the solution has to be to set GIT_ASKPASS to run a process that the parent process
can receive the credentials requests from via a pipe/socket. Then I can pop up a dialog to ask for
credentials and pass them to git (I could also save in a Wallet for later use).

Is this something you would add and support in GitPython?

Ah, interesting ! I think you should be able to set custom environment variables per call or for all calls on each repository's git instance. That way you can provide your own program to bring up some GUI to collect the login data for you as needed.

Regarding this issue: I wouldn't know what to do about it ... can you clarify ?

I think that you should consider handling the credentials side of GIT in the GitPython code.

For this it looks like you need a executable that you point GIT_ASKPASS at.
Before running GIT in a subprocess you would setup GIT_ASKPASS and open a
pair of unix domain sockets/Windows Named Pips to send and receive the data
from the program in GIT_ASKPASS.

That program will read its stdin and write that into GitPythons pipe. GitPython calls a
auth_callback with the details (username or password
and URL). The callback returns the answer and GitPython writes it into the pipe for
hte GIT_ASPPASS program to output on stdout.

Is that the clarification you wanted?

It seems this issue turned from a question and possibly a description of an issue (i.e. missing error description from git.push) into a specific feature request.

As to me GitPython is in maintenance mode and will only receive bugfixes or merges of suitable PRs, I flagged this issue as help wanted.

Maybe with you possibly implementing GIT_ASKPASS already, you might eventually see how the created code could integrate with GitPython to make it more useful to everyone.

I'll experiment with solution in git-workbench and when I have something useful I will create a PR for you.