Compatible with pulsar-all based on ubuntu 20.04 #270
Description
Due to the base image of pulsar-all comes from ubuntu 20.04 (apache/pulsar#11026), some images may be incompatible with the new pulsar-all image. For example, the build process of pulsar-functions-python-runner image will be broken because it requires python3.7, python3.7-dev and libreadline-gplv2-dev, which are not available on ubuntu 20.04.