Why this error when I try to create workspaces in ROS?

Question

Whenever I try to create a workspace:

~/catkin_ws$ catkin_make

It shows like this:

ImportError: "from catkin_pkg.package import parse_package" failed: No module named 'catkin_pkg'
Make sure that you have installed "catkin_pkg", it is up to date and on the PYTHONPATH.
CMake Error at /opt/ros/kinetic/share/catkin/cmake/safe_execute_process.cmake:11 (message):
  execute_process(/home/usuario/miniconda3/bin/python
  "/opt/ros/kinetic/share/catkin/cmake/parse_package_xml.py"
  "/opt/ros/kinetic/share/catkin/cmake/../package.xml"
  "/home/usuario/catkin_ws/build/catkin/catkin_generated/version/package.cmake")
  returned error code 1
Call Stack (most recent call first):
  /opt/ros/kinetic/share/catkin/cmake/catkin_package_xml.cmake:63 (safe_execute_process)
  /opt/ros/kinetic/share/catkin/cmake/all.cmake:151 (_catkin_package_xml)
  /opt/ros/kinetic/share/catkin/cmake/catkinConfig.cmake:20 (include)
  CMakeLists.txt:52 (find_package)


-- Configuring incomplete, errors occurred!
See also "/home/usuario/catkin_ws/build/CMakeFiles/CMakeOutput.log".
See also "/home/usuario/catkin_ws/build/CMakeFiles/CMakeError.log".
Invoking "cmake" failed

It seems like there is a problem with catkin_pkg but I dont find the solution

Answer 1

I just installed ROS on Ubuntu 16.04, had the same issue, and fixed it. The location for catkin_pkg is likely not on your PYTHONPATH and needs to be added.

From the error output:

Make sure that you have installed "catkin_pkg", it is up to date and on the PYTHONPATH.

Try locating catkin_pkg and check your PYTHONPATH. catkin_pkg wasn't on my PYTHONPATH (likely due to other program installs), so I added it and ran catkin_make again, this time successfully.

~/catkin_ws$ locate catkin_pkg
/usr/lib/python2.7/dist-packages/catkin_pkg

~/catkin_ws$ echo $PYTHONPATH
/opt/ros/kinetic/lib/python2.7/dist-packages

To append the catkin_pkg dir to PYTHONPATH (for this session):

~/catkin_ws$ export PYTHONPATH=$PYTHONPATH:/usr/lib/python2.7/dist-packages

For permanency I appended the catkin_pkg dir to PYTHONPATH in my .bashrc (you might want to backup your .bashrc file first, e.g. cp -p ~/.bashrc ~/.bashrc-ros-catkin.bak).

To do this, edit your ~/.bashrc file (you might need to use sudo to edit this file) and add the following two lines to the end of the file:

# manually added for ROS catkin_make workspace setup
export PYTHONPATH=$PYTHONPATH:/usr/lib/python2.7/dist-packages

Save the file and run source to update your session:

~/catkin_ws$ source ~/.bashrc

Check your PYTHONPATH again:

~/catkin_ws$ echo $PYTHONPATH
/opt/ros/kinetic/lib/python2.7/dist-packages:/usr/lib/python2.7/dist-packages

Obviously the location of your catkin_pkg files might be different to mine, so use that path instead when appending to $PYTHONPATH above.

Now try running catkin_make again. If you get the same error, paste the output of your catkin_pkg location and PYTHONPATH here.

Cheers, sb