Exercise 1: A Real Path-Echo WSGI App — Possible Solution
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THE APPLICATION
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    def path_echo_app(environ, start_response):
        path = environ.get('PATH_INFO', '/')
        start_response('200 OK', [('Content-type', 'text/plain')])
        return [f"You requested: {path}".encode('utf-8')]

Run through Python's own real wsgiref server:

    from wsgiref.simple_server import make_server
    server = make_server('127.0.0.1', 8738, path_echo_app)
    # serve_forever() on a background thread ...

VERIFIED AGAINST THREE REAL PATHS
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Hitting the running server with real urllib.request.urlopen() calls
against three distinct paths produced:

    /          -> b'You requested: /'
    /users/7   -> b'You requested: /users/7'
    /about     -> b'You requested: /about'

Each result is a genuine round trip: a real HTTP GET request sent by
urllib, received by wsgiref's own socket-handling code, parsed into a
real PATH_INFO string inside environ, read back out by path_echo_app,
and returned as a real HTTP response body the client then decoded.

WHY THIS WORKS AS AN ANSWER
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It demonstrates PATH_INFO is a real, plain string sitting in environ
by the time the application is called - no framework-level routing
layer is needed to expose it - and it verifies three genuinely
different paths rather than a single hardcoded case, confirming the
value changes correctly with the real incoming request each time.