Comment 2 for bug 1942937

@jameinel informed me that the general goal is to eliminate absolute local paths for charms in bundles, as well as limit relative paths to being a subdirectory of wherever bundle.yaml lives. He also pointed me towards bundle zips, which are simple zip files with a bundle.yaml at the root level, as well as any relevant charm artifacts.

Zipping everything up into a bundle works in general, but exhibits the same behavior as this bug. I have a bundle.yaml that references the included charms as e.g. `./istio-gateway_ubuntu-20.04-amd64.charm`, and get this error when deploying it:

$ juju deploy ./bundle.zip
Executing changes:
- upload charm istio-gateway from local for series focal with architecture=amd64
ERROR cannot deploy bundle: cannot deploy local charm at "istio-gateway": file does not exist