Perhaps I've been too concise. If so, I apologise. My proposal is that the system be set up so that debug(a, b, c) sends output to the correct stream, whatever it should be.
Python 3.7 includes the new built-in breakpoint() function as an easy and consistent way to enter the Python debugger.
So I'm suggesting a new built-in debug() function as an easy and consistent way to write out debugging information.