gh-140458: Clarify xmlrpc.client behavior

[Yzi-Li]

Fails or ProtocolError are raised as exceptions, not returned.

• Issue: xmlrpc.client tells Fails and ProtocolError are returned, while the code raises them #140458

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📚 Documentation preview 📚: https://cpython-previews--140759.org.readthedocs.build/

[Yzi-Li]

Requesting @JulienPalard. TiA!

[JulienPalard]

@Yzi-Li Thanks for the PR, looks good to me!

[bedevere-bot]

⚠️⚠️⚠️ Buildbot failure ⚠️⚠️⚠️

Hi! The buildbot AMD64 FreeBSD Refleaks 3.x (tier-3) has failed when building commit ed81baf.

What do you need to do:

1. Don't panic.
2. Check the buildbot page in the devguide if you don't know what the buildbots are or how they work.
3. Go to the page of the buildbot that failed (https://buildbot.python.org/#/builders/1613/builds/2357) and take a look at the build logs.
4. Check if the failure is related to this commit (ed81baf) or if it is a false positive.
5. If the failure is related to this commit, please, reflect that on the issue and make a new Pull Request with a fix.

You can take a look at the buildbot page here:

https://buildbot.python.org/#/builders/1613/builds/2357

Failed tests:

• test.test_concurrent_futures.test_process_pool

Test leaking resources:

• test_subprocess: references
• test_subprocess: memory blocks
• test_process_pool: file descriptors
• test_process_pool: memory blocks
• test_process_pool: references

Summary of the results of the build (if available):

==

Click to see traceback logs

Traceback (most recent call last):
  File "/buildbot/buildarea/3.x.ware-freebsd.refleak/build/Lib/test/support/__init__.py", line 847, in gc_collect
    gc.collect()
    ~~~~~~~~~~^^
ResourceWarning: unclosed file <_io.FileIO name=11 mode='wb' closefd=True>
Xtest_cancel_make_subprocess_transport_exec (test.test_asyncio.test_subprocess.SubprocessPidfdWatcherTests.test_cancel_make_subprocess_transport_exec) ... skipped 'operating system does not support pidfds'


Traceback (most recent call last):
  File "/buildbot/buildarea/3.x.ware-freebsd.refleak/build/Lib/test/support/__init__.py", line 847, in gc_collect
    gc.collect()
    ~~~~~~~~~~^^
ResourceWarning: unclosed <socket.socket fd=10, family=2, type=1, proto=6, laddr=('127.0.0.1', 37020), raddr=('127.0.0.1', 37021)>
Task was destroyed but it is pending!
task: <Task pending name='Task-89' coro=<BaseSelectorEventLoop._accept_connection2() done, defined at /buildbot/buildarea/3.x.ware-freebsd.refleak/build/Lib/asyncio/selector_events.py:217> wait_for=<Future pending cb=[Task.task_wakeup()]>>
Warning -- Unraisable exception
Exception ignored while calling deallocator <function _SelectorTransport.__del__ at 0x83f1dab10>:
Traceback (most recent call last):
  File "/buildbot/buildarea/3.x.ware-freebsd.refleak/build/Lib/asyncio/selector_events.py", line 873, in __del__
    _warn(f"unclosed transport {self!r}", ResourceWarning, source=self)
    ~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
ResourceWarning: unclosed transport <_SelectorSocketTransport closing fd=10>
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