Error in using rqt_graph in Kinetic

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When I use the command

rosrun rqt_graph rqt_graph

I get this error:

Traceback (most recent call last):
  File "/opt/ros/kinetic/lib/rqt_graph/rqt_graph", line 5, in <module>
    from rqt_gui.main import Main
  File "/opt/ros/kinetic/lib/python2.7/dist-packages/rqt_gui/main.py", line 38, in <module>
    import rospy
  File "/opt/ros/kinetic/lib/python2.7/dist-packages/rospy/__init__.py", line 49, in <module>
    from .client import spin, myargv, init_node, \
  File "/opt/ros/kinetic/lib/python2.7/dist-packages/rospy/client.py", line 47, in <module>
    import yaml
  File "/usr/lib/python2.7/dist-packages/yaml/__init__.py", line 2, in <module>
    from error import *
ImportError: No module named 'error'

I use Ubuntu 16.04 and ROS Kintic