Pin to Python 3.11.

[bdice]

Pin devcontainers to Python 3.11.

During the migration to Python 3.12, we are getting py=3.12 as a matrix selector for rapids-dependency-file-generator, which in turn selects python=3.12 for repositories that have added support. However, for repositories that have not migrated yet, we get the fallback matrix python>=3.10,<3.12 which conflicts with the other pinning. To avoid this, we can pin devcontainers to use PYTHON_VERSION="3.11" which will be passed through to the logic here:

devcontainers/features/src/rapids-build-utils/opt/rapids-build-utils/bin/make-conda-dependencies.sh

Lines 62 to 73 in f9155e8

	local python_version="${PYTHON_VERSION:-$(python3 --version 2>&1 | cut -d' ' -f2)}";
	python_version="$(cut -d'.' -f3 --complement <<< "${python_version}")";
	local -a _matrix_selectors=(
	arch="$(uname -m)"
	cuda="${cuda_version}"
	py="${python_version}"
	);
	# add extra arguments (if there are conflicts, e.g. 'py=3.10;py=3.11', it's fine... the last one will win)
	test ${#matrix_entry[@]} -gt 0 && _matrix_selectors+=("${matrix_entry[@]}");
	local -r matrix_selectors=$(IFS=";"; echo "${_matrix_selectors[*]}")

[jameslamb]

Thanks for looking into this!

I hadn't considered the way that Python version detection here would have been silently hitting the fallback matrices until at least one repo had a match.

I've updated rapidsai/build-planning#40 with checklist items so when we go to add Python 3.13 in the future, we remember to do this again.