Fix API.request_url() with Py3.13 (#208)

Since Python 3.13, the IOBase finalizer now logs
any errors raised by the close() method
https://docs.python.org/3/whatsnew/3.13.html#io

According to
https://docs.python.org/3.13/library/io.html#io.IOBase.close
if the file (descriptor) is accessed after being close,
`ValueError` is raised.

The `fd` is copied with `copy.copy()`.
Both gets automatically closed once the function ends,
the second can’t close a second time the same fd,
that’s why we get this error.

Reorganise complex function: don’t use `with` since the function
is designed to allow returning the fd
Drop `copy.copy()` used previously to return the fd, causing the issue
Cleanly separate three return types and function’s returns