Reject the POETRY_VIRTUALENVS_IN_PROJECT env var too (#566)

Since it's another Poetry related env var that shouldn't be set
by the end user since it can break builds.

See:
https://python-poetry.org/docs/configuration/#virtualenvsin-project

GUS-W-22400354.

Author: edmorley

CHANGELOG.md

@@ -12,6 +12,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - Updated pip from 26.0.1 to 26.1.1. ([#563](https://github.com/heroku/buildpacks-python/pull/563))
 - Updated Poetry from 2.3.4 to 2.4.0. ([#564](https://github.com/heroku/buildpacks-python/pull/564))
 - Updated uv from 0.11.6 to 0.11.11. ([#562](https://github.com/heroku/buildpacks-python/pull/562))
+- The forbidden env vars check now also rejects `POETRY_VIRTUALENVS_IN_PROJECT`. ([#566](https://github.com/heroku/buildpacks-python/pull/566))
 
 ## [6.4.1] - 2026-04-13
 

src/checks.rs

@@ -20,6 +20,7 @@ const FORBIDDEN_ENV_VARS: &[&str] = &[
     "POETRY_DATA_DIR",
     "POETRY_HOME",
     "POETRY_VIRTUALENVS_CREATE",
+    "POETRY_VIRTUALENVS_IN_PROJECT",
     "POETRY_VIRTUALENVS_USE_POETRY_PYTHON",
     "PYTHONHOME",
     "PYTHONINSPECT",