Use alpine images instead of Python. (#290)

* Use alpine images instead of Python.

* Minor fix to use python3 -m pip

* Fix settings for paintstore.

core/Dockerfile

@@ -1,4 +1,4 @@
-FROM python:3.6-alpine
+FROM alpine:3.8
 
 MAINTAINER Abhilash Raj
 
@@ -7,10 +7,11 @@ COPY docker-entrypoint.sh /usr/local/bin/
 
 #Install all required packages, add user for executing mailman and set execution rights for startup script
 RUN apk update \
-    && apk add --virtual build-deps gcc python3-dev musl-dev postgresql-dev libffi-dev \
-    && apk add bash su-exec postgresql-client mysql-client curl \
-	&& pip install -U pip \
-    && pip install psycopg2 \
+	&& apk add --virtual build-deps gcc python3-dev musl-dev postgresql-dev \
+	   libffi-dev \
+	&& apk add --no-cache bash su-exec postgresql-client mysql-client curl python py3-setuptools \
+	&& python3 -m pip install -U pip \
+    && python3 -m pip install psycopg2 \
                    mailman==3.2 \
                    mailman-hyperkitty==1.1.0 \
                    pymysql \