macport pip install Cryptography/pyOpenSSL报错 Expected in: flat namespace

如题，macport pip安装pyOpenSSL过程中，要安装依赖包Cryptography，在该依赖包中，报错，经过不懈的查询，找到这篇文章 http://chriskief.com/2014/03/25/installing-cryptography-via-pip-with-macports-or-homebrew/comment-page-1/#comment-2809

按照作者的方案，要增加几个环境变量再pip，如下

sudo env ARCHFLAGS=“-arch x86_64” LDFLAGS=“-L/opt/local/lib” CFLAGS=“-I/opt/local/include” pip install cryptography

记录并分享一下，再次感谢原作者Chris Kief