fix(docker): Define python/python3 alias for every image

[ovr]

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[claude]

Claude finished @ovr's task in 39s —— View job

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Code Review

Verdict: LGTM — 0 high, 0 medium, 1 low.

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Summary

Replaces the Debian python3 metapackage with an explicit python3.13 install across all Dockerfiles, and uses update-alternatives to register both /usr/bin/python3 and /usr/bin/python aliases pointing at python3.13. This makes the python command available (needed by node-gyp on some paths) and pins the exact interpreter version rather than relying on Debian's default. The same three-line pattern is applied consistently in every build/final stage.

Observations

• Applied consistently to all 5 Dockerfiles and both the build and final stages where relevant — nice.
• Removing the python3 metapackage is fine: python3.13 provides the interpreter, and update-alternatives re-establishes the /usr/bin/python3 symlink previously provided by the metapackage. No packages in these images depend on the metapackage.
• packages/cubejs-docker/testing-drivers.Dockerfile line 16 — the build stage now installs python3.13 but not libpython3.13-dev, while the final stage does. This matches the prior behavior (build stage didn't install a -dev package either), so it's not a regression, just noting for consistency with the other Dockerfiles which pair them together in the build stage.

Low

• Priority 1 in update-alternatives --install ... 1 is very low. If any future package registers a higher-priority alternative for python3, it would silently take over. Not a bug today, but bumping to a higher value (e.g. 100, which matches Debian's own convention for python3.x alternatives) would make the intent stickier. Applies to all five Dockerfiles.

Nits

• In latest-debian-jdk.Dockerfile and latest.Dockerfile, the comment # libpython3-dev is needed to trigger post-installer to download native with python is now the sole leftover from the removed comment pair — reads a little oddly on its own but is still accurate.
  • Branch: fix/python-alias