I've never heard of the 'empty python3-google-compute-engine transitional package'; for upstream packaging, we use "Conflicts: python3-google-compute-engine" and this will cause the top level package (called google-compute-engine upstream, I think called gce-compute-image-packages in Ubuntu) to be skipped in upgrades, and an administrator would have to issue dist-upgrade to enable the automatic removal of the conflicting package.
I've never heard of the 'empty python3- google- compute- engine transitional package'; for upstream packaging, we use "Conflicts: python3- google- compute- engine" and this will cause the top level package (called google- compute- engine upstream, I think called gce-compute- image-packages in Ubuntu) to be skipped in upgrades, and an administrator would have to issue dist-upgrade to enable the automatic removal of the conflicting package.