fix: Fix broken logger statement in parse_requirements.bzl

[mark-thm]

parse_requirements.bzl includes a broken logger statement by passing a string instead of a lambda. The result is that when a hash is no longer available on pypi (say, due to a release being yanked) that rules_python causes Bazel to halt. Since we use Bazel to generate requirements files, this means the only solution is to use non-Bazel tooling to get back to a functional state before then running Bazel tooling to update the requirements file -- all down to a faulty log statement.

This PR corrects the faulty log statement. A more thorough fix might be to update the logger to warn if its invoked with a string instead of a lambda rather than failing.

An example traceback which led to this discovery:

ERROR: Traceback (most recent call last):
	File ".../external/rules_python~/python/private/bzlmod/pip.bzl", line 472, column 52, in _pip_impl
		is_hub_reproducible = _create_whl_repos(module_ctx, pip_attr, hub_whl_map, whl_overrides, hub_group_map, simpleapi_cache)
	File ".../external/rules_python~/python/private/bzlmod/pip.bzl", line 187, column 50, in _create_whl_repos
		requirements_by_platform = parse_requirements(
	File ".../external/rules_python~/python/private/parse_requirements.bzl", line 348, column 37, in parse_requirements
		whls, sdist = _add_dists(
	File ".../external/rules_python~/python/private/parse_requirements.bzl", line 452, column 24, in _add_dists
		logger.warn("Could not find a whl or an sdist with sha256={}".format(sha256))
	File ".../external/rules_python~/python/private/repo_utils.bzl", line 78, column 39, in lambda
		warn = lambda message_cb: _log(0, "WARNING", message_cb),
	File ".../external/rules_python~/python/private/repo_utils.bzl", line 72, column 71, in _log
		print("\nrules_python: {}: ".format(level.upper()), message_cb())  # buildifier: disable=print
Error: 'string' object is not callable

[rickeylev]

Thanks for the fix! I pushed an update to the changelog.

I wonder if there's a similar error a couple lines below, in the if yanked branch? It looks like logger can be None, but it unconditionally calls logger there.

[aignas]

Thanks for the PR. Logger might be None only in tests, but I'll go through the code once more to see if there are more places like this.