Error executing roslaunch turtlebot_bringup minimal.launch --screen

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Please help!

roslaunch turtlebot_bringup minimal.launch --screen

... logging to /home/ahmed/.ros/log/7230a1cc-2af0-11e6-8726-74e543e0ae3e/roslaunch-ahmed-HP-ENVY-dv7-Notebook-PC-5114.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/indigo/share/xacro/xacro.py", line 60, in <module> import xacro File "/opt/ros/indigo/lib/python2.7/dist-packages/xacro/__init__.py", line 45, in <module> from roslaunch import substitution_args File "/opt/ros/indigo/lib/python2.7/dist-packages/roslaunch/__init__.py", line 48, in <module> import rospkg ImportError: No module named rospkg while processing /opt/ros/indigo/share/turtlebot_bringup/launch/includes/robot.launch.xml: while processing /opt/ros/indigo/share/turtlebot_bringup/launch/includes/description.launch.xml: Invalid tag: Cannot load command parameter [robot_description]: command [/opt/ros/indigo/share/xacro/xacro.py '/opt/ros/indigo/share/turtlebot_description/robots/kobuki_hexagons_asus_xtion_pro.urdf.xacro'] returned with code [1].

Param xml is The traceback for the exception was written to the log file