fixup! CI: use debian stable instead of ubuntu bionic and drop python2

CI/Dockerfile

-FROM ubuntu:bionic
+FROM debian:stable
 
 ENV HOME=/root
+ENV TZ=Europe/Prague
 ENV LC_ALL=en_US.utf8
+ENV DEBIAN_FRONTEND=noninteractive
 
 # Install base packages
+# TODO once bullseye becomes stable remove the backports
 RUN \
   sed -i 's/# \(.*multiverse$\)/\1/g' /etc/apt/sources.list && \
+  echo "deb http://deb.debian.org/debian buster-backports main" > /etc/apt/sources.list.d/backports.list && \
   echo "# Installing base packages" && \
   apt-get update && \
   apt-get -y upgrade && \
   apt-get -y install --no-install-recommends \
     lua5.1 liblua5.1-0-dev libjson-c-dev \
     git cmake make pkg-config gcc g++ openssh-client \
-    python-prctl python-dev python-setuptools python-pip \
     python3-prctl python3-dev python3-setuptools python3-pip \
     locales \
     && \
   apt-get clean
 
+# Set Timezone
+RUN \
+  rm -f /etc/localtime && \
+  echo "$TZ" > /etc/timezone && \
+  dpkg-reconfigure -f noninteractive tzdata
+
+# Update python paths
+RUN \
+  update-alternatives --install /usr/bin/python python /usr/bin/python3 1 && \
+  update-alternatives --install /usr/bin/pip pip /usr/bin/pip3 1
+
 # Generate locales
 RUN \
   echo "en_US.UTF-8 UTF-8" > /etc/locale.gen && \
   locale-gen
 
-# Use updated version of some core python packages
-#RUN \
-#  pip install --upgrade pip && \
-#  pip install --upgrade setuptools
-
 # Compile libubox
 RUN \
   mkdir -p ~/build && \
@@ -36,7 +45,7 @@ RUN \
   git clone git://git.openwrt.org/project/libubox.git && \
   cd ~/build/libubox && \
   git checkout master && \
-  cmake CMakeLists.txt && \
+  cmake CMakeLists.txt -DCMAKE_INSTALL_PREFIX:PATH=/usr && \
   make install
 
 # Compile ubus
@@ -44,19 +53,15 @@ RUN \
   mkdir -p ~/build && \
   cd ~/build && \
   rm -rf ubus && \
-  git clone https://gitlab.labs.nic.cz/turris/ubus.git && \
+  git clone https://gitlab.nic.cz/turris/ubus.git && \
   cd ~/build/ubus && \
-  git checkout python_bindings && \
-  cmake CMakeLists.txt -DBUILD_PYTHON='ON' && \
-  make && \
-  cmake CMakeLists.txt -DBUILD_PYTHON='OFF' && \
-  make install && \
-  cd python && \
-  pip install --upgrade .
+  git checkout master && \
+  cmake CMakeLists.txt -DCMAKE_INSTALL_PREFIX:PATH=/usr && \
+  make install
 
 # Add Gitlab's SSH key
 RUN \
   mkdir /root/.ssh && \
-  ssh-keyscan gitlab.labs.nic.cz > /root/.ssh/known_hosts
+  ssh-keyscan gitlab.nic.cz > /root/.ssh/known_hosts
 
 CMD [ "bash" ]