为什么在使用python 2.7.12的最新paramiko 2.0.2时，它会报告一个错误RequirementParseError无效的需求解析错误

I use python 2.7.12 and newest paramiko 2.0.2, and run a script which ssh login many linux server concurrently.I use python 2.7.12 and newest paramiko 2.0