By: Lucien Huber <im@lcnbr.ch>
build the dev shell's python3 and virtualenv as one environment The dev shell listed `virtualenv`, built for Nixpkgs' default Python (3.14), next to `linnetPython` (3.13). Python's setup hook put 3.14's site-packages, which hold its `_sysconfigdata`, on PYTHONPATH, so the shell's python3 reported 3.14's sysconfig. pyo3 then configured a 3.13 build that links libpython3.14, and embedded-Python tests such as feynkit-ufo's `forwards_options_and_deserializes_json` aborted. Provide both as `linnetPython.withPackages`. The environment brings no setup hook, so PYTHONPATH stays unset and every interpreter, including venvs and uv-managed Pythons, reads its own sysconfig. nix-ci.nix keeps enable = false during review. Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>