Notification when starting debugging and no interpreter has been selected

If you start debugging and no environment is selected, you just get an error with no explanation.

I suggest if no Python environment is selected, we pop up a notification:

You need to select a Python interpreter before you start debugging. 
Tip: click on "Select Python Environment" in the status bar.

[ Select Python Interpreter ] 

[qubitron]

Also I noticed the select python environment is not visible in your gif, is there anyway to have that take priority over the other items in the status bar?

[qubitron]

Let’s go without the weird behavior and no button, at least that way the user for sure will learn how to use the interpreter selector!