[Python-ideas] wsgiref.simple_server should mount and serve a provided WSGI application script

[Masklinn]

Many (most?) WSGI servers use WSGI application scripts (a Python script with a `.py` or `.wsgi` extension generally, providing a global `application` variable) to setup and mount applications.

Currently, `python -m wsgiref.simple_server` mounts a trivial "hello world" application and opens it in the web browser.

It would be nice if `python -m wsgiref.simple_server file` mounted and served the application set up by the script instead.