make posix_sitl_default gazebo出现Required python packages not installed

编译出现问题：

python import error: No module named ‘em’
Required python packages not installed.
On a Debian/Ubuntu system please run:

sudo apt-get install python-empy
sudo pip install catkin_pkg

On MacOS please run:
sudo pip install empy catkin_pkg

On Windows please run:
easy_install empy catkin_pkg

方法：

链接：https://blog.csdn.net/sinat_21190681/article/details/83508442

运行

python -m pip install empy 

问题消失