`scenarios.json` does not support running with existing features

[AlexanderLanin]

Observation

When ghcr.io/devcontainers/features/python:1 is added as a feature to scenarios.json, it attempts to read local file path: '/workspaces/my-feature/src/ghcr.io/devcontainers/features/python:1'.

Expectation

It will use python feature for testing. Therefore I would see that it behaves correctly regarding installsAfter and my stuff can indeed use python.

Background:

my-feature requires python 3.7, therefore I implemented a version detection in case the available version is too old. However as there is a python feature already, I don't want to add too much complex logic to my script. I have an error message which tells people to use https://github.com/devcontainers/features/tree/main/src/python in addition to my-feature.
However I cannot verify that this would indeed work!

[joshspicer]

Yes, this was also raised in #217 and is good to point out.

The test command currently injects the appropriate relative path for all Features in the scenario, so this is not expected to work (But I agree would be very handy!)