setuptools 82 removed pkg_resources

A GitHub Actions job deploys AWS infrastructure with Pulumi’s Python SDK. Each run makes a new virtualenv and installs infra/requirements.txt. One morning the staging deploy failed, and nothing in the repo had changed:

ModuleNotFoundError: No module named 'pkg_resources'

The traceback ended in pulumi_aws/_utilities.py, at import pkg_resources. pkg_resources came with setuptools, and setuptools 82.0.0 removed it. The requirements file didn’t pin setuptools, so the fresh virtualenv got 82, and the pinned pulumi-aws==5.41.0 still imports the module.

Pinning setuptools below the release that removed it fixed the deploy:

# infra/requirements.txt
setuptools<81
pulumi-aws==5.41.0

The pin keeps deploys working with the provider version already in use. Newer provider versions don’t import pkg_resources, so upgrading the provider removes the need for it. A lock file for the infra dependencies, from uv or pip-tools, keeps a new setuptools from showing up on its own.