輸入 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.
解決方法
sudo apt-get install python-rosdep python-wstool ros-kinetic-ros
先安裝上面三個東西，ros-kinetic-ros應該是肯定有的，我缺的是中間的python-wstool，裝完再運行sudo rosdep init就可以了