bpo-35015: Doc: Fix internationalisation of the availability directive.

[JulienPalard]

I don't really understand why we have to give the content twice (once as a parameter of the node, and once as child of the node) but that's what's the BaseAdmonition directive does:

Add it first as a text parameter of the node:

admonition_node = self.node_class(text, **self.options)

then add the content as child of the node:
self.state.nested_parse(self.content, self.content_offset,
admonition_node)

so I did the same and it works.

https://bugs.python.org/issue35015

https://bugs.python.org/issue35015

[JulienPalard]

DO-NOT-MERGE tag while I'm running a diff of generated pot files.

[JulienPalard]

Diff is nice:

< msgid "Availability: Unix, Windows.  spawnlp(), spawnlpe(), spawnvp() and spawnvpe() are not available on Windows.  spawnle() and spawnve() are n
ot thread-safe on Windows; we advise you to use the subprocess module instead."
---
> msgid ":ref:`Availability <availability>`: Unix, Windows.  :func:`spawnlp`, :func:`spawnlpe`, :func:`spawnvp` and :func:`spawnvpe` are not availa
ble on Windows.  :func:`spawnle` and :func:`spawnve` are not thread-safe on Windows; we advise you to use the :mod:`subprocess` module instead."

[miss-islington]

Thanks @JulienPalard for the PR 🌮🎉.. I'm working now to backport this PR to: 3.7.
🐍🍒⛏🤖

[bedevere-bot]

GH-10399 is a backport of this pull request to the 3.7 branch.