Python artifacts download auth issues when building ADK agent example apps

[jacobsimionato]

I'm getting an issue like this:

(cd a2a_agents/python/adk/samples/restaurant_finder/; uv run .)

  × Failed to build `a2ui-restaurant-finder @
  │ file:///Users/jsimionato/development/A2UI/a2a_agents/python/adk/samples/restaurant_finder`
  ├─▶ Failed to resolve requirements from `build-system.requires`
  ├─▶ No solution found when resolving: `hatchling`
  ╰─▶ Because hatchling was not found in the package registry and you require hatchling, we can conclude
      that your requirements are unsatisfiable.

      hint: An index URL (https://us-python.pkg.dev/artifact-foundry-prod/ah-3p-staging-python/simple/)
      could not be queried due to a lack of valid authentication credentials (401 Unauthorized).

To fix it, I had to do some combination of

• Install keyring stuff shown at https://docs.cloud.google.com/artifact-registry/docs/python/authentication e.g.

  uv pip install keyring
  uv pip install keyrings.google-artifactregistry-auth
  

• install gcloud and run glcoud auth login

I'm not sure which of the above were necessary.

We should either update our READMEs to mention this, or somehow make it so that it isn't necessary. Ideally, this code will be as accessible to developers as possible.