message: change base image to tensorflow:custom-op
diff: -FROM ubuntu:18.04
  +FROM tensorflow/tensorflow:custom-op
  RUN apt-get update && \
  apt-get install -y \
  - build-essential \
  curl \
  nano \
  unzip \
  ffmpeg
  -ARG BAZEL_VERSION=0.20.0
  +ARG BAZEL_VERSION=0.24.1
  ARG BAZEL_OS=linux
  RUN curl -sL https://github.com/bazelbuild/bazel/releases/download/${BAZEL_VERSION}/bazel-${BAZEL_VERSION}-installer-${BAZEL_OS}-x86_64.sh -o bazel-install.sh && \
  @@ -39,6 +38,7 @@ RUN /bin/bash -c "source activate tfio-dev && python -m pip install \
  pytest \
  pylint \
  boto3 \
  + google-cloud-pubsub==0.39.1 \
  pyarrow==${ARROW_VERSION} \
  pandas \
  ${PIP_ADD_PACKAGES} \
  