[×××.launch]is neither a launch file in package [××] nor is [××] a launch file name解决办法

错误描述：[×××.launch]is neither a launch file in package [××] nor is [××] a launch file name. The traceback for the exception was written to the file

解决办法：

cd ~/catkin_ws
source devel/setup.bash

catkin_ws 是你的工作空间的名称，但是这样只是暂时解决了，本次有效。
一劳永逸的解决办法是：
打开.bashrc文件

gedit ~/.bashrc

把下面这句话添加进去，保存文件

source ~/catkin_ws/devel/setup.bashrc

再在终端执行

source ~/.bashrc