Broken `python` target due to missing external repo

[z8v]

The python target relies on the @python repo which is not included in the dependencies.

Seems like we need a config option that will configure a python toolchain and make it available for the target.

Using the following MODULE.bazel file from the readme is enough to re-produce it, with an empty WORKSPACE and BUILD.bazel file.

# Boost
# Famous C++ library that has given rise to many new additions to the C++ Standard Library
# Makes @boost available for use: For example, add `@boost//:algorithm` to your deps.
# For more, see https://github.com/nelhage/rules_boost and https://www.boost.org
bazel_dep(name = "rules_boost", repo_name = "com_github_nelhage_rules_boost")
archive_override(
    module_name = "rules_boost",
    strip_prefix = "rules_boost-master",
    urls = "https://github.com/nelhage/rules_boost/archive/refs/heads/master.tar.gz",
    # It is recommended to edit the above URL and the below sha256 to point to a specific version of this repository.
    # integrity = "sha256-...",
)

non_module_boost_repositories = use_extension("@com_github_nelhage_rules_boost//:boost/repositories.bzl", "non_module_dependencies")
use_repo(
    non_module_boost_repositories,
    "boost",
)

$ bazel build @boost//:python
ERROR: no such package '@@[unknown repo 'python' requested from @@rules_boost~~non_module_dependencies~boost]//': The repository '@@[unknown repo 'python' requested from @@rules_boost~~non_module_dependencies~boost]' could not be resolved: No repository visible as '@python' from repository '@@rules_boost~~non_module_dependencies~boost'
...

Worth adding bazel build @boost//... on the CI as well when this is fixed.