Fix path remaining as none + formatting code

[rsclip]

Changes are detailed in 2 commits. Essentially I fixed the code to suit Python's naming conventions (adding docstrings, constant variable names, etc.) and also added a safety measure where if PATH is still none after calling shutil.which() (which I assume takes it from %path%), it uses spotify's default installation directory.

To elaborate on it you could get a list of installed programs, select Spotify and get the directory from there but this is a simple small approach.

[AnonymouX47]

@Cyclip Sorry, the conflicts here are already pretty much. Please can you open another PR with the formatting changes made on a new branch of an updated fork. 🙏🏾

Try following these steps:

1. Close this PR.
2. Delete your own fork of the repo (from it's "settings").
3. Create a new fork,
4. Create a new branch (i.e in your fork).
5. Make the changes.
6. Open a PR requesting to merge the new branch (having the change) with upstream's main.

I said you should delete your fork because trying to fetch from upstream to your current fork will result in merge conflicts because you made changes on your fork's main branch. 👍🏾