Request
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* Subiquity is shipped as a core20-based snap today. Make it a core22-based snap for 23.04
Why Needed
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* LXD is transitioning to core22 for 23.04.
* In an effort to keep a single core in the live installer, we should build subiquity against core22 as well.
What Changed
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* Subiquity builds against core22. This means all the build and stage dependencies are picked from jammy/jammy-updates rather than focal/focal-updates.
* The version of python used as runtime switches from python3.8 to python3.10 for subiquity, curtin, probert and other third party dependencies such as ubuntu-advantage-tools & ssh-import-id.
Build Test
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https://launchpad.net/~canonical-foundations/+snap/test/+build/2052291
Other testing
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* Full server install ran successfully on a jammy ISO with injected core22-based snap
* Full server install ran successfully on a lunar ISO with injected core22-based snap
* Unit tests and integration tests have been running against a core22-like environment since the development phase of 22.04, so we already have some degree of confidence.
Other info
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* Some testing had already been performed by the ubuntu-desktop-installer running on core22.
Code to merge
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https://github.com/canonical/subiquity/pull/1597
FFe granted. It's risky, but we still have time before the beta.