When installing something, in my case Discord.js, you can often run into an error saying that Python can't be found, even when you're sure that it's installed. I had infact installed it twice, and it still didn't work. Navigating to the directory that it says it can't find Python in, will often end up with you finding Python there. Setting the PYTHON Environment Variable doesn't change anything.
The image below is an example of the error:
Steps to solve the issue (Installing Windows Build Tools):
Below is a picture of the solution, after it's complete. (Still need to install the dependencies)