在跑《Ros by Example 1中通过模拟器来测试控制机器人，并在rviz上显示效果其中终端输入下面命令时：
roslaunch rbx1_bringup fake_turtlebot.launch报错：
... logging to /home/mallikarjun/.ros/log/47f3e6c2-6153-11e7-9730-9439e5050f5a/roslaunch-mallikarjun-Ideapad-Z570-21214.log Checking log directory for disk usage. This may take awhile. Press Ctrl-C to interrupt Done checking log file disk usage. Usage is <1GB.
Traceback (most recent call last): File "/opt/ros/lunar/share/xacro/xacro.py", line 55, in <module> import xacro File "/opt/ros/lunar/lib/python2.7/dist-packages/xacro/__init__.py", line 35, in <module> import glob File "/home/mallikarjun/anaconda3/lib/python3.6/glob.py", line 4, in <module> import re
ModuleNotFoundError: No module named 're'
Invalid tag: Cannot load command parameter [robot_description]: command [/opt/ros/lunar/share/xacro/xacro.py '/home/mallikarjun/mybot_ws/src/mybot_description/urdf/mybot.xacro'] returned with code [1].、
类似这样的错误，主要原因是：
我安装的anaconda3使用的Python版本没有分清楚，配环境的时候有点混用，Python2.7和3.6不清楚所致。
解决方法：
暂时将.bashrc文件中关于anaconda的环境配置先注释掉
sudo gedit ~/.bashrc然后Ctrl+F搜索anaconda的内容，一般也就集中在一起，然后注释掉。更新一下
source ~/.bashrc然后重新实验 就ok了
参考文献：https://answers.ros.org/question/265455/modulenotfounderror-no-module-named-re/?sort=latest