Could not fetch URL https://pypi.python.org/simple/opencv-python/: There was a problem confirming the ssl certificate: [SSL: CERTIFICATE_VERIFY_FAILED] certificate verify failed (_ssl.c:661) - skipping
证书问题
1. 升级 pip
pip 本身都要问题，故 pip install pip 不可用
手动安装
steps:
1. https://pypi.org/project/pip/
2. 解压
tar -zxvf
3. python setup.py install
4. success
2. 跳过 ssl 校验
使用一下命令安装
pip --trusted-host pypi.python.org install <包名>
