Update Dockerfile

Dockerfile

 FROM ubuntu
 WORKDIR /opt/strudel2/src
 COPY . /opt/strudel2/src
-RUN apt update
-RUN apt install -y python3 gcc python3-pip
-RUN apt install -y openssh-client
-RUN pip3 install -r requirements.txt
-RUN python3 ./setup.py install
+RUN apt update && apt install -y python3 gcc python3-pip openssh-client
+RUN set -x \
+	&& addgroup -g 33 -S www-data \
+	&& adduser -u 33 -D -S -G www-data www-data
+RUN pip3 install -r requirements.txt && python3 ./setup.py install
 EXPOSE 8080 8090
 CMD ["./runscript"]