message: docker: switch image to ubuntu bionic
diff: -FROM rust:slim
  +FROM ubuntu:bionic
  ### STEP 1: Install dependencies ###
  # Install packaged dependencies
  RUN apt-get update && apt-get install -y --no-install-recommends \
  build-essential git curl cmake gcc g++ pkg-config libmagic-dev \
  - libssl-dev zlib1g-dev sudo docker.io
  + libssl-dev zlib1g-dev sudo ca-certificates docker.io
  +
  +# Install the stable toolchain with rustup
  +RUN curl https://static.rust-lang.org/rustup/dist/x86_64-unknown-linux-gnu/rustup-init >/tmp/rustup-init && \
  + chmod +x /tmp/rustup-init && \
  + /tmp/rustup-init -y --no-modify-path --default-toolchain stable
  +ENV PATH=/root/.cargo/bin:$PATH
  ### STEP 2: Setup build environment as new user ###
  RUN mkdir -p /opt/docsrs/prefix
  