Cannot plot turtle pose in rqt_plot

edit

Hi All! I am just starting to learn ROS. So I was following the tutorial on understanding TOPICS ( http://wiki.ros.org/ROS/Tutorials/Und... ), where I was supposed to run $ rosrun rqt_plot rqt_plot and enter /turtle1/pose/x in GUI, but I keep getting this message in the terminal:

    Traceback (most recent call last):   File "/opt/ros/hydro/lib/python2.7/dist-packages/rqt_plot/plot_widget.py", line 204, in on_topic_edit_textChanged
        plottable, message = is_plottable(topic_name)   File "/opt/ros/hydro/lib/python2.7/dist-packages/rqt_plot/plot_widget.py", line 104, in is_plottable
        fields, message = get_plot_fields(topic_name)   File "/opt/ros/hydro/lib/python2.7/dist-packages/rqt_plot/plot_widget.py", line 75, in get_plot_fields
        field_class = topic_helpers.get_type_class(slot_type) AttributeError: 'module' object has no attribute 'get_type_class'
AttributeError: 'module' object has no attribute 'get_type_class'

I ran roswtf and got this :

Loaded plugin tf.tfwtf
No package or stack in context
================================================================================
Static checks summary:

Found 1 error(s).

ERROR Not all paths in PYTHONPATH [/home/omar/catkin_ws/devel/lib/python2.7/dist-packages:/opt/ros/hydro/lib/python2.7/dist-packages] point to a directory: 
 * /home/omar/catkin_ws/devel/lib/python2.7/dist-packages

================================================================================
Beginning tests of your ROS graph. These may take awhile...
analyzing graph...
... done analyzing graph
running graph rules...
... done running graph rules

Online checks summary:

No errors or warnings

I can't get any plots described in tutorials, so I was hoping you could help.