教程中下载过程会很慢
sudo apt install ros-noetic-desktop-full，这个把网络切成流量热点就能变快了。
- 解决python3和ros不兼容导致catkin_make失败问题
（这里是用了catkin_make -DPYTHON_EXECUTABLE=/usr/bin/python3这个命令catkin_make解决的） - rospack Error: package 'learning_xxxx' not found
(solve this error by using another terminator and commandingsource devel/setup.bash)