PyQt 5.9.2 appears broken about fbs-tutorial

[bicarlsen]

I think it may be helpful to state it a bit more forcefully too. Something like

Only Python versions 3.5 and 3.6 are supported. Other versions will likely give errors.

on it's own line.

[mherrmann]

I'll try to make the following from the README even clearer:

The only prerequisite is Python 3.5 or 3.6. Python 3.7 is not yet officially supported. It may or may not work.

[bicarlsen]

This appears to only be an issue for Python version above 3.6, I haven't tested the exact version at which it breaks. However, because this is a tutorial, and it appears one of the most common errors is to use an incompatible Python version, it may be worth mentioning somewhere in the tutorial the required Python versions.