ImportError pkg_resources & pkg six In RaspberryPi

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i want to install ROS fuerte in raspberry pi

when i use command

rosinstall --catkin ~/ros-underlay http:/ /ros.org/rosinstalls/fuerte-ros-full.rosinstall

error :

pi@raspberrypi ~ $ rosinstall --catkin ~/ros-underlay http: //ros.org/rosinstalls/fuerte-ros-full.rosinstall

Traceback (most recent call last): File "/usr/local/bin/rosinstall", line 5, in <module> from rosinstall.rosinstall_cli import rosinstall_main File "/usr/local/lib/python2.7/dist-packages/rosinstall/__init__.py", line 33, in <module> import wstool.helpers File "/usr/local/lib/python2.7/dist-packages/wstool/helpers.py", line 37, in <module> from wstool.config_elements import SetupConfigElement File "/usr/local/lib/python2.7/dist-packages/wstool/config_elements.py", line 38, in <module> from vcstools.vcs_abstraction import get_vcs_client File "/usr/local/lib/python2.7/dist-packages/vcstools/__init__.py", line 44, in <module> from vcstools.svn import SvnClient File "/usr/local/lib/python2.7/dist-packages/vcstools/svn.py", line 44, in <module> import dateutil.parser # For parsing date strings File "/usr/local/lib/python2.7/dist-packages/dateutil/parser.py", line 24, in <module> from six import text_type, binary_type, integer_types ImportError: No module named six

please i need help , thanks