PEP 621 style virtualenv.

.envrc

+PYTHON_VERSION="$(python3 -c 'from sys import version_info as v; print(f"{v[0]}.{v[1]}")')"
+export PYTHONPATH="$PWD/__pypackages__/$PYTHON_VERSION:${PYTHONPATH:-}"
+export PATH="$PWD/__pypackages__/$PYTHON_VERSION/bin:$PATH"
+python3 -m pip install -t "__pypackages__/$PYTHON_VERSION" -e .

MANIFEST.in

@@ -3,3 +3,4 @@ include *.txt
 exclude .pre-commit-config.yaml
 exclude .gitlab-ci.yml
 exclude .gitignore
+exclude .env*