Thanks for sharing this!
I wanted to make sure it would work with my network, so I went through the work to run the python script. I haven't used python before, so here's what I went through from a noobs perspective (may be useful to someone else)
Downloaded python 3.7.2 (I think) from python website. Opened IDLE python 3.7.2 shell (start -> python -> IDLE python). Then I copy pasted the script you posted in the main post. Hitting enter gave an error on the second line of code, hilighting "include sys". (It was probably a different problem explained below)
I ended up downloading another compiler/environment to try. I downloaded PyCharm. I created a new python program, named it 90dnstester.py like what you pasted, then ran it. (From top bar, select run). It gave a more reasonable error that I needed to install "pip install dnspython". I didn't know how to do that. I downloaded dnspython (not dnspython3) and tried typing into PyCharm "pip install dnspycharm" as it said, knowing it has no idea where those files are downloaded. Obviously it failed. I couldn't figure out how to install, so I unzipped the dnspython download and started copy pasting it into each folder of the PyCharm install. (I believe it worked after pasting in the c:/users/(your user)/python directory tree.). Then tried rerunning 90dnstester.py and it worked!
I probably could have just pasted the dnspython files into the python directory and ran it through the stock IDLE Python software, but whatever
Hope this helps another noob like me make sure the network is safe!
Comcast ISP, Surfboard modem, Netgear router.