输入 sudo rosdep init
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.
解决方法
sudo apt-get install python-rosdep python-wstool ros-kinetic-ros
先安装上面三个东西，ros-kinetic-ros应该是肯定有的，我缺的是中间的python-wstool，装完再运行sudo rosdep init就可以了