When something weird happens

ROS has several tools to detect potential problems in all the elements of a given package. Just move with roscd to the package you want to analyze. Then, run roswtf. For chapter3_tutorials, we have the following output. Note that if you have something running, the ROS graph would be analyzed too. We run the roslaunch chapter3_tutorials example6.launch command that yields the an output similar to the following screenshot:

In general, we should expect no error or warning, but even some of them are innocuous. In the preceding screenshot, we see that roswtf does not detect any error; it only issues a warning about pip, which sometimes might generate problems with the Python code installed in the system. Note that the purpose of roswtf is to signal potential problems, and then we are responsible to check whether they are real or meaningless ones, as in the previous case.

Another useful tool is catkin_lint, which helps to diagnose errors with catkin, usually in the CMakeLists...