fix binder v0.16

Dockerfile

@@ -10,7 +10,7 @@ RUN apt install -y curl
 
 # install dependencies - including the stable version of Gammapy
 COPY binder.py tmp/
-RUN curl -o tmp/environment.yml https://gammapy.org/download/install/gammapy-0.18.2-environment.yml
+RUN curl -o tmp/environment.yml https://gammapy.org/download/install/gammapy-0.16-environment.yml
 
 WORKDIR tmp/
 RUN conda update conda
@@ -29,16 +29,16 @@ RUN adduser --disabled-password \
     ${NB_USER}
 
 # download tutorials and datasets
-RUN gammapy download notebooks --out=${HOME}/gammapy-tutorials --release=0.18.2
-RUN gammapy download datasets --out=${HOME}/gammapy-datasets --release=0.18.2
+RUN gammapy download notebooks --out=${HOME}/gammapy-tutorials --release=0.16
+RUN gammapy download datasets --out=${HOME}/gammapy-datasets --release=0.16
 
 # setting ownerships
 USER root
 RUN chown -R gammapy:gammapy ${HOME}
 
 # start JupyterLab server in tutorials dir
 USER ${NB_USER}
-WORKDIR ${HOME}/gammapy-tutorials/notebooks-0.18.2
+WORKDIR ${HOME}/gammapy-tutorials/notebooks-0.16
 
 # env vars used in tutorials
 ENV GAMMAPY_DATA ${HOME}/gammapy-datasets