improve install poetry in venv

install_poetry_in_venv.sh

@@ -1,6 +1,9 @@
+# This script installs poetry within its own venv the way
+# it is when deployed so that its deps are isolated from the deps of the projects it manages
 rm -fr poetry_env
 poetry build
 python -m venv poetry_env
 touch poetry_env/poetry_env
 poetry_env/bin/pip install dist/poetry-1.5.2-py3-none-any.whl
-# need to edit poetry_env/bin/poetry shebang line
+# inspired by https://stackoverflow.com/a/584926:
+sed -i 's@/usr/bin/env python3@'"$REPL_HOME"'/poetry_env/bin/python3@g' poetry_env/bin/poetry