[launch] is neither a launch file in package [urdf_sim_tutorial] nor is [urdf_sim_tutorial] a launch

在运行官网所给的命令时，出现[launch] is neither a launch file in package [urdf_sim_tutorial] nor is [urdf_sim_tutorial] a launch file name
The traceback for the exception was written to the log file

官网给的命令是 roslaunch urdf_sim_tutorial 13-diffdrive.launch

具体问题是环境没有设置

在当前包所放置的环境下，到/dev中找到 setup.bash 文件，  然后source一下就可以了。