如果 roslaunch beginner_tutorials turtlemimic.launch 發現
[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說類似於：No such package/stack 'beginner_tutorials'你需要啓動環境變量設置的文件，像你之前在create_a_workspace教程末尾中做的一樣。
$ 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說類似於：No such package/stack 'beginner_tutorials'你需要啓動環境變量設置的文件，像你之前在create_a_workspace教程末尾中做的一樣。
$ cd ~/catkin_ws
$ source devel/setup.bash
$ roscd beginner_tutorials
如果一直出現這個問題，
爲了保證每次打開bash的時候，保證workspace在環境中
在終端中輸入命令行gedit ~/.bashrc
會彈出一個文件在末尾處加上
source ~/dev/catkin_ws/devel/setup.bash
注意上面是我們的目錄，每個人可能不太一樣
我的是上面的。
然後再保存退出再重複剛纔的roslaunch beginner_tutorials turtlemimic.launch
會出現如下所示，並彈出兩個小烏龜窗口哦（成功）
