Revert breaking changes to rocker_rpy

Author: Robinlovelace

rocker-rpy/Dockerfile

@@ -1,8 +1,16 @@
 FROM ghcr.io/geocompx/minimal
 
+# Use Python already provisioned by the base image virtualenv (/opt/venv).
+# Do not reinstall Python; ensure the venv python is preferred and 'python' exists.
+RUN /rocker_scripts/install_python.sh
+
+# Prefer the venv python and put its bin on PATH so reticulate picks it up.
+ENV RETICULATE_PYTHON=/opt/venv/bin/python
+ENV PATH=/opt/venv/bin:${PATH}
+
 # Small helper so the 'python' command exists (doesn't reinstall python itself).
-RUN apt-get update && apt-get install -y --no-install-recommends python-is-python3 python3-pip \
-    && rm -rf /var/lib/apt/lists/*
+RUN apt-get update && apt-get install -y --no-install-recommends python-is-python3 \
+	&& rm -rf /var/lib/apt/lists/*
 
-# Install project requirements into the existing venv if desired:
-RUN python3 -m pip install -r https://github.com/geocompx/geocompy/raw/refs/heads/main/requirements.txt --break-system-packages
+# Optionally install project requirements into the existing venv if desired:
+RUN /opt/venv/bin/pip install -r https://github.com/geocompx/geocompy/raw/refs/heads/main/requirements.txt