Since this may be unclear without actually inspecting the image, a common way to diagnose something like this is to run the image with an alternative command, such as /bin/sh, and use an interactive session to look around and do your validation and debugging. You can do this locally if you have Docker installed; when you do so, make sure you explicitly override the entrypoint and command to run a command interactively:
docker run -it --entrypoint=/bin/sh \quay.io/kubernetes-for-developers/flask:latest -i
You can then manually invoke what the container would have run, python3 /opt/exampleapp/exampleapp, and do any additional debugging there.
You can do this same thing in a Kubernetes cluster, if you don't ...