At the time of article posting (2019/11/27), when running PyInstaller with Python 3.8, the following error occurs
TypeError: an integer is required (got type bytes)
This is because PyInstaller3.5, which is the current (2019/11/27) stabilizer, does not support Python3.8.
Download the Development version. If you install with pip, it is as follows.
pip install https://github.com/pyinstaller/pyinstaller/archive/develop.tar.gz