Errors with the latest kivy 2.0.0 release

[ghoshsuman]

While running mustard.py, I get the following error (invalid "horizontal" Orientation value), which I believe is due to the changes in the latest release of Kivy in October 2020:

The error happened because I used the provided requirements.txt to install dependencies. I was able to run it when I downgraded to kivy=1.11.1 (which explicitly needs python < 3.8). An update of the requirements or the code according to new Kivy would help.