You are using Raspbian Jessie. This version is deprecated and its support has finished last year. Also the tutorial you are using notes in section
Development and Target Platforms
. Operating Systems
.... Raspbian* Buster, 32-bit
.... Raspbian* Stretch, 32-bit
Raspbian Jessie does not match this condition so what you try cannot work. You should ...
That what @Milliways wrote in his answer. To answer your question about testing for bad blocks on the SD Card: you cannot test it, simply while a SD Card does not have blocks. It has cells with limited live time for writing it. SD Cards today have spare cells that will be used on the fly for defected cells and a logic will always show you a proper SD Card ...