Standarize image by using shared / similair layers

services/fetchmail/Dockerfile

@@ -1,7 +1,11 @@
-FROM python:3-alpine
-
+FROM alpine:3.8
+# python3 shared with most images
+RUN apk add --no-cache \
+    python3 py3-pip \
+  && pip3 install --upgrade pip
+# Image specific layers under this line
 RUN apk add --no-cache fetchmail ca-certificates \
- && pip install requests
+ && pip3 install requests
 
 COPY fetchmail.py /fetchmail.py
 USER fetchmail

services/fetchmail/fetchmail.py

@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/python3
 
 import time
 import os