alpine3.12镜像必须指明python版本
apk add --update --no-cache py-pip python3 bash
apk add --no-cache python2 && \
参考网址:https://github.com/Docker-Hub-frolvlad/docker-alpine-python2/commit/78cd4c0674cf42d7fe7d973c5595b42a76f0d969