如果 roslaunch beginner_tutorials turtlemimic.launch 发现
[turtlemimic.launch] is neither a launch file in package [beginner_tutorials] nor is [beginner_tutorials] a launch file name
The traceback for the exception was written to the log file
如果$ roscd beginner_tutorials命令roscd说类似于： No such package/stack 'beginner_tutorials'你需要启动环境变量设置的文件，像你之前在create_a_workspace教程末尾中做的一样。
$ cd ~/catkin_ws
$ source devel/setup.bash
[turtlemimic.launch] is neither a launch file in package [beginner_tutorials] nor is [beginner_tutorials] a launch file name
The traceback for the exception was written to the log file
如果$ roscd beginner_tutorials命令roscd说类似于： No such package/stack 'beginner_tutorials'你需要启动环境变量设置的文件，像你之前在create_a_workspace教程末尾中做的一样。
$ cd ~/catkin_ws
$ source devel/setup.bash
$ roscd beginner_tutorials
如果一直出现这个问题，
为了保证每次打开bash的时候，保证workspace在环境中
在终端中输入命令行gedit ~/.bashrc
会弹出一个文件在末尾处加上
source ~/dev/catkin_ws/devel/setup.bash
注意上面是我们的目录，每个人可能不太一样
我的是上面的。
然后再保存退出再重复刚才的roslaunch beginner_tutorials turtlemimic.launch
会出现如下所示，并弹出两个小乌龟窗口哦（成功）
