Fix test validators for Python 3
A couple of tests are failing with Python 3 because of a small problem in the Python code used for the test validators.
This MR fixes the tests in a backward (Python 2) compatible way.
Edited by Marco Clemencic
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A couple of tests are failing with Python 3 because of a small problem in the Python code used for the test validators.
This MR fixes the tests in a backward (Python 2) compatible way.