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.

Close #208 (closed).