I'm programming a python toolbox (*.pyt) and want to display a progressbar in arcgis 10.3. I'm using the same piece of code as this one, but I can't see the same dialog box as above. I can only see the messages updating in the geoprocessing "results" window. I also tried to add my Pyt to the toolbox window, but this didn't solve this issue.
Is this progressor class only working for python script, and not for python toolbox ?