[Python-Dev] Add a developer mode to Python: -X dev command line option

[Victor Stinner]

Ok, I merged my PR adding -X dev: you can now test in Python 3.7 ;-)

> The list of checks can be extended later. For example, we may enable
> the debug mode of asyncio: PYTHONASYNCIODEBUG=1.

I opened https://bugs.python.org/issue32047 to propose enable asyncio
debug mode using the Python developer mode.

What do you think? Is it ok to include asyncio in the global "developer mode"?

Victor