rqt_graph error (Could not import "pyqt" bindings of qt_gui_cpp library - so C++ plugins will not be available)

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Hi, I am doing the 'Understanding ROS Topics' tutorial and was following these instructions specifically: http://wiki.ros.org/ROS/Tutorials/Und... . Everything worked fine until I tried to run rosrun rqt_graph rqt_graph. No graph appeared and I got a lengthy error message beginning with Could not import "pyqt" bindings of qt_gui_cpp library - so C++ plugins will not be available and ending with ImportError: No module named pydot. I suspected that the problem was related to Anaconda, so I ran conda install pydot. I ran rosrun rqt_graph rqt_graph again and a graph actually appeared, but I still got this shorter error message:

Could not import "pyqt" bindings of qt_gui_cpp library - so C++ plugins will not be available:
Traceback (most recent call last):
  File "/opt/ros/kinetic/lib/python2.7/dist-packages/qt_gui_cpp/cpp_binding_helper.py", line 43, in <module>
    import libqt_gui_cpp_sip
ImportError: /home/perrin/anaconda2/lib/python2.7/site-packages/PyQt5/../../../libstdc++.so.6: version `GLIBCXX_3.4.20' not found (required by /opt/ros/kinetic/lib/python2.7/dist-packages/qt_gui_cpp/libqt_gui_cpp_sip.so)

I tried running conda install pyqt but this didn't help. I'm using ROS Kinetic and Ubuntu Xenial on an x86_64, with kernel 4.4.0.