Clarify some assumptions in the pyinstaller tutorial

[SirGnip]

Documentation tweak

What documentation needs to change?

The pyinstaller tutorial initial "quickstart" could be more explicit.
https://arcade.academy/tutorials/bundling_with_pyinstaller/index.html

What is wrong with it? How can it be improved?

This tutorial makes some assumptions about the Python environment that is being used. I'll get a PR up shortly.

[pvcraven]

Docs at this point should already be up.