mac上突然无法安装python库，Could not fetch URL https://pypi.python.org/simple/django/

今天需要用python virtualenv创建一个隔离环境，在安装django的时候一直提示无法找到匹配的pypi版本

提示如下：

(venv-myproject) ➜  ~ pip install Django==1.10.8
Collecting Django==1.10.8
  Could not fetch URL https://pypi.python.org/simple/django/: There was a problem confirming the ssl certificate: [SSL: TLSV1_ALERT_PROTOCOL_VERSION] tlsv1 alert protocol version (_ssl.c:590) - skipping
  Could not find a version that satisfies the requirement Django==1.10.8 (from versions: )
No matching distribution found for Django==1.10.8

issue title: Problem Confirming the SSL Certificate - OSX #5236
方案地址：https://github.com/pypa/pip/issues/5236
解决命令：curl https://bootstrap.pypa.io/get-pip.py | python