Fixes canonical/snapcraft#6524 If creating the Launchpad repo failed, we assumed it already existed and looked it up. When it didn't exist (e.g. Launchpad returned a 503), users got "Could not find repository" and the real error was lost. Now, if the lookup finds nothing or fails too, we raise a RemoteBuildError with the original HTTP status and reason, and suggest retrying for 5xx responses. I ran ruff, ty, codespell and the full test suite in a Linux container rather than `make lint && make test`. No new failures: the tests that fail there fail on main too. --- - [x] I've followed the [contribution guidelines](https://github.com/canonical/craft-application/blob/main/CONTRIBUTING.md). - [x] I've signed the [CLA](http://www.ubuntu.com/legal/contributors/). - [ ] I've successfully run `make lint && make test`. - [ ] I've added or updated any relevant documentation. - [ ] In documents I changed, I [added a meta description](https://canonical-starflow.readthedocs-hosted.com/how-to/add-a-page-meta-description/) if one was missing. - [x] I've updated the relevant release notes.