5. 通过Dockerfile安装python

1. mkdir -p ~/python ~/python/myapp

2. 创建Dockerfile文件
   FROM buildpack-deps:jessie

remove several traces of debian python

RUN apt-get purge -y python.*

http://bugs.python.org/issue19846

> At the moment, setting “LANG=C” on a Linux system fundamentally breaks Python 3, and that’s not OK.

ENV LANG C.UTF-8

gpg: key F73C700D: public key “Larry Hastings larry@hastings.org” imported

ENV GPG_KEY 97FC712E4C024BBEA48A61ED3A5CA953F73C700D

ENV PYTHON_VERSION 3.5.1