removed xenial docker container. Is not build any more and docker build is failing lately

dockerfiles/xenial.docker

-FROM ubuntu:xenial
-ENV http_proxy http://xfelproxy.desy.de:3128
-ENV https_proxy http://xfelproxy.desy.de:3128
-ENV DEBIAN_FRONTEND noninteractive
-
-RUN apt-get update && \
-    apt-get install -y software-properties-common apt-utils && \
-    add-apt-repository -y universe && \
-    add-apt-repository -y ppa:hola-launchpad/valgrind && \
-    add-apt-repository -y ppa:git-core/ppa && \
-    add-apt-repository -y ppa:edd/misc && \
-    apt-get update && \
-    apt-get upgrade -y && \
-    apt-get dist-upgrade -y && \
-    apt-get install -y sudo wget python3-pip locales && \
-    apt-get install -y g++ valgrind cppcheck lcov doxygen procmail make git gdb cmake ninja-build && \
-    apt-get install -y libboost-all-dev libxml++2.6-dev && \
-    apt-get install -y libldap2-dev libzmq3-dev rpcbind && \
-    apt-get install -y libreadline-dev && \
-    apt-get install -y libqt4-dev qtbase5-dev && \
-    apt-get install -y python2.7-dev python-numpy python3-dev python3-numpy && \
-    apt-get install -y python-pytest && \
-    apt-get install -y libxmu6 csh libxrandr2 && \
-    apt-get install -y libncurses5-dev && \
-    apt-get install -y linux-headers-generic && \
-    apt-get install -y graphviz && \
-    apt-get install -y clang-8 && \
-    apt-get install -y libhdf5-dev && \
-    apt-get install -y liblua5.2-dev && \
-    apt-get install -y python-sphinx && \
-    apt-get install -y libgsl-dev && \
-    apt-get install -y libssl-dev && \
-    apt-get install -y libpqxx-dev && \
-    apt-get install -y libfftw3-dev && \
-    apt-get install -y subversion && \
-    apt-get install -y vim-common && \
-    apt-get install -y netcat-openbsd && \
-    apt-get install -y libarmadillo-dev && \
-    apt-get install -y libjsoncpp-dev && \
-    apt-get install -y python3-pytest && \
-    apt-get install -y libxerces-c-dev && \
-    apt-get install -y libmuparser-dev && \
-    useradd -u 30996 msk_jenkins && \
-    ln -sfn /usr/lib/x86_64-linux-gnu/libzmq.so.5 /usr/lib/x86_64-linux-gnu/libzmq.so.3 && \
-    pip3 install pip --upgrade && \
-    pip install meson ninja
-
-RUN echo "Defaults set_home" >> /etc/sudoers && \
-    echo 'Acquire::http::proxy "http://xfelproxy.desy.de:3128/";' > /etc/apt/apt.conf && \
-    echo 'http_proxy=http://xfelproxy.desy.de:3128' >> /etc/environment && \
-    echo 'https_proxy=https://xfelproxy.desy.de:3128' >> /etc/environment && \
-    git config --system http.proxy http://xfelproxy.desy.de:3128 && \
-    git config --system https.proxy http://xfelproxy.desy.de:3128
-
-# NOTE: This last line (symlink for libzmq.so.3) is a hack for a bug in DOOCS serverlib, which has the version number hardcoded.
-
-ADD lcov-to-cobertura-xml /common/lcov_cobertura-1.6
-
-# Start rpcbind at launch of the container, required for DOOCS
-ENTRYPOINT ["bash", "-c", "rpcbind -f -w ; bash"]