mention Graphviz dependency #14

Author: ceteri

Dockerfile

@@ -4,10 +4,10 @@ ENV LANGUAGE en_US.UTF-8
 ENV LC_ALL en_US.UTF-8
 ENV LANG en_US.UTF-8
 
-
 COPY requirements.txt requirements.txt
 RUN python3 -m pip install -U pip
 RUN python3 -m pip install -r requirements.txt
+RUN apt install graphviz
 
 ENV WORKDIR /ray_tutorial
 WORKDIR ${WORKDIR}

README.md

@@ -53,6 +53,10 @@ Note: if you run into any problems on Python 3.8 with "wheels"
 during a `pip` installation, you may need to use the `conda`
 approach instead.
 
+For some of the visualizations in `pi.ipynb` you also need to
+[install graphviz](https://graphviz.org/download/#executable-packages)
+
+
 Then launch the [JupyterLab](https://jupyterlab.readthedocs.io/) 
 environment to run examples in this repo:
 ```bash