update python3-alpine

python3-alpine/Dockerfile

 FROM alpine
 RUN echo "https://mirror.tuna.tsinghua.edu.cn/alpine/v3.4/main/" > /etc/apk/repositories 
-RUN apk update --no-cache\
-		&& apk add --no-cache python3
+RUN apk update --no-cache \
+    && apk add --no-cache python3 \
+    && cd /usr/bin \
+    && ln -sf pip3 pip \
+    && mkdir -p /root/.pip \
+	&& echo -e '[global]\nindex_url = https://pypi.doubanio.com/simple' > /root/.pip/pip.conf \
+    && pip install --upgrade --no-cache-dir pip
 
-RUN cd /usr/bin \
-		&& ln -sf pip3 pip