Hack: explictly in stall graphviz early

Author: andreas-zeller

binder/Dockerfile

@@ -34,6 +34,10 @@ RUN apt-get install -y git python3 python-is-python3 pip npm gcc
 # Some version info
 RUN echo "This is ${PROJECT} with $(python --version)" 1>&2
 
+# Install graphviz
+# We do this now to get informed about any errors
+RUN apt-get install -y graphviz libgraphviz-dev
+
 # Install jupyter
 RUN pip install --no-cache --upgrade pip && \
     pip install --no-cache notebook jupyterlab