No package 'libffi' found
系统没有安装必须的开发包的缘故。一般多见于Debian系系统.
解决方案:
apt-cache search libffi | grep dev
apt-get install libffi-dev
...
还是没有相关依赖包,应该只用安装一个就可以了
apt-get install python3-dev
参考链接:http://raspberrypi.stackexchange.com/questions/37281/cant-install-flask-bcrypt-libffi-is-missing
http://stackoverflow.com/questions/28363514/when-i-try-to-install-flask-bcrypt-it-throws-me-error-command-x86-64-linux-gnu
