Inspecting stdout of a rc!=0 container called with run(detach=False)

Trying to run a container, I was getting a non-zero return code (because the container was missing a variable for the process inside the container to complete successfully), and was wondering how to inspect stdout and stderr of the container. The following is my attempt:

import docker
client = docker.from_env()

try:
    out, err = client.containers.run(image="some_image_that_fails", stdout=True, stderr=True)
except Exception as e:
    print(e)

Running like this, I only get stderr, not stdout though.

Is this intended? It's perhaps a philosofical question whether the stdout should be returned when there's an error... I also figured out that you can get both if you run with detach=True - but should this be necessary?

I believe the responsible line is this line in models/container.py where the output that is part of the exceptions arguments raised for non-zero return code is set to only stderr.

Read models/containers.py at the linked line where the non-zero return-code exception output is set. Compare run(detach=False) with detach=True and verify that a failing container makes both stdout and stderr available through the exception; no test file is named in the issue.