update dockerfile

docker/Dockerfile

@@ -1,6 +1,9 @@
 FROM maven:3.8.6-openjdk-8 as builder
 
 WORKDIR /workspace
+RUN sed -i "s@http://\(deb\|security\).debian.org@https://mirrors.aliyun.com@g" /etc/apt/sources.list
+RUN apt update && apt install -y python3 python3-pip python-is-python3 \
+    && pip config set global.index-url https://mirror.nju.edu.cn/pypi/web/simple
 ADD . .
 RUN mkdir -p ~/.m2 && cp -r docker/settings.xml ~/.m2
 RUN wget http://mirror.nju.edu.cn/apache/spark/spark-3.1.3/spark-3.1.3-bin-hadoop3.2.tgz