Troubleshooting

Note: You might not get the exact same errors listed here but the general error type (e.g. no module, invalid package, etc.) should be able to be resolved with a similar solution as noted below

Error 1:

Command: roslaunch ...

Error:

ModuleNotFoundError: No module named 're'
while processing /opt/ros/kinetic/share/turtlebot_bringup/launch/includes/robot.launch.xml:
while processing /opt/ros/kinetic/share/turtlebot_bringup/launch/includes/description.launch.xml:
Invalid <param> tag: Cannot load command parameter [robot_description]: command [/opt/ros/kinetic/share/xacro/xacro.py '/opt/ros/kinetic/share/turtlebot_description/robots/kobuki_hexagons_asus_xtion_pro.urdf.xacro'] returned with code [1]. 

Param xml is <param command="$(arg urdf_file)" name="robot_description"/>
The traceback for the exception was written to the log file

Solution: change python export path in .bashrc (reference)

cd
sudo gedit .bashrc

Change export PATH=/home/yourusername/anaconda3/bin:$PATH to export PATH=/home/yourusername:$PATH then open a new terminal and try again

Error 2:

Command: roslaunch ...

Error:

[nav_turtle_sim.launch] is neither a launch file in package [nav_turtle] nor is [nav_turtle] a launch file name
The traceback for the exception was written to the log file

Solution: Edit .bashrc to include correct ROS package path

cd
sudo gedit .bashrc

Add line export ROS_PACKAGE_PATH=~/catkin_ws/src:/opt/ros/kinetic/share to the end of the file, open a new terminal, and try again

Error 3:

Command: roslaunch ...

Error:

Invalid <arg> tag: environment variable 'NAV_TURTLE_MAP_FILE' is not set. 

Arg xml is <arg default=" $(env NAV_TURTLE_MAP_FILE)" name="map_file"/>
The traceback for the exception was written to the log file

Solution: Edit .bashrc to source catkin workspace

cd
sudo gedit .bashrc

Add line source ~/catkin_ws/devel/setup.bash to the end of the file and open a new terminal to try again