message: Add apt-get update --fix-missing to Dockerfile.
  * This fixes the problem of "Undetermined Error [IP: 91.189.88.142 80]".
  #codehealth
diff: # (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
  # OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  +# Build instructions with this Dockerfile.
  +# https://github.com/google/mozc/blob/master/docs/build_mozc_in_docker.md
  +
  FROM ubuntu:20.04
  ENV DEBIAN_FRONTEND noninteractive
  # Package installation
  -RUN apt-get update
  +RUN apt update --fix-missing
  +RUN apt upgrade -y
  ## Common packages for linux build environment
  -RUN apt-get install -y clang libc++-dev libc++abi-dev python python-six python3-six pkg-config git curl bzip2 unzip make ninja-build
  +RUN apt-get install -y clang libc++-dev libc++abi-dev python3 pkg-config git curl bzip2 unzip make ninja-build
  ## Packages for linux desktop version
  RUN apt-get install -y libibus-1.0-dev libglib2.0-dev qtbase5-dev libgtk2.0-dev libxcb-xfixes0-dev
  ## Packages for misc tools
  