If the polar_demo.py script (matplotlib folder) is executed and a zoom is done, the displayed coordinate information contains greek letters. They raised an UnicodeError in backend_itom.py (def set_message). A workaround fixed the exception, however the special characters are currently encoded as hex-numbers. Maybe, it is possible to really display them.
Originally copied from: https://bitbucket.org/itom/itom/issues/57/matplotlib-show_message-encoding-error