pip install selenium安装报错：Could not build wheels for cryptography which use PEP 517 and cannot be installed directly
1.terminal 控制台 pip升级报错：AttributeError: ‘NoneType’ object has no attribute ‘bytes’
1、解决方法：
方法一：升级pip
easy_install -U pip
方法二;强制安装pip
python -m pip install -U --force-reinstall pip
2、安装selenium**
pip install selenium -i https://pypi.douban.com/simple
