title: ImportError: No module named catkin_pkg.packages
body: <p>I am trying to run:-<br>
  roslaunch turtlebot_gazebo turtlebot_world.launch</p>
  
  <p>but I am getting following error</p>
  
  <pre><code>Traceback (most recent call last):
    File "/opt/ros/kinetic/share/xacro/xacro.py", line 55, in &lt;module&gt;
      import xacro
    File "/opt/ros/kinetic/lib/python2.7/dist-packages/xacro/__init__.py", line 42, in &lt;module&gt;
      from roslaunch import substitution_args
    File "/opt/ros/kinetic/lib/python2.7/dist-packages/roslaunch/__init__.py", line 56, in &lt;module&gt;
      from .launch import ROSLaunchRunner
    File "/opt/ros/kinetic/lib/python2.7/dist-packages/roslaunch/launch.py", line 55, in &lt;module&gt;
      from roslaunch.nodeprocess import create_master_process, create_node_process
    File "/opt/ros/kinetic/lib/python2.7/dist-packages/roslaunch/nodeprocess.py", line 49, in &lt;module&gt;
      from roslaunch.node_args import create_local_process_args
    File "/opt/ros/kinetic/lib/python2.7/dist-packages/roslaunch/node_args.py", line 53, in &lt;module&gt;
      import roslib.packages
    File "/opt/ros/kinetic/lib/python2.7/dist-packages/roslib/__init__.py", line 54, in &lt;module&gt;
      import roslib.stacks
    File "/opt/ros/kinetic/lib/python2.7/dist-packages/roslib/stacks.py", line 46, in &lt;module&gt;
      import roslib.packages
    File "/opt/ros/kinetic/lib/python2.7/dist-packages/roslib/packages.py", line 49, in &lt;module&gt;
      from catkin.find_in_workspaces import find_in_workspaces as catkin_find
    File "/opt/ros/kinetic/lib/python2.7/dist-packages/catkin/find_in_workspaces.py", line 36, in &lt;module&gt;
  
  
  from catkin_pkg.packages import find_packages
  ImportError: No module named catkin_pkg.packages
  while processing /opt/ros/kinetic/share/turtlebot_gazebo/launch/includes/kobuki.launch.xml:
  Invalid &lt;param&gt; 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]. 
  </code></pre>