参考：https://www.cnblogs.com/xuhaoforwards/p/9399744.html
安装ROS过程中运行sudo rosdep init后，出现如下错误LOG：
ERROR: cannot download default sources list from: https://raw.githubusercontent.com/ros/rosdistro/master/rosdep/sources.list.d/20-default.list Website may be down.
解决办法
sudo apt-get install python-wstool
NVidia Jetson Ubuntu 18.04 安装ROS过程中运行sudo rosdep init指令出错
原文：https://www.cnblogs.com/xbit/p/11399526.html