Documentation

The.. availability:: directives in our documentation do not use a consistent syntax. The arguments are all over the place. For example versions are indicate asLinux >= 4.2,Linux 4.2 and newer, orLinux 4.2 or later. Some directives have additional content that point to man pages. Others reference minimum versions although we no longer support the version (e.g.FreeBSD 9 or later although FreeBSD 9 is not supported any more).

I would like to make the availability directive arguments consistent and parsable:

• Use consistent spelling for version restrictionsplatform >= version.
• Introducenot prefix to indicate that a feature is not available on that platform.
• Check for known platform strings and emit a warning when a platform is not in an allow list.
• Enablehas_content for the directive and move all additional remarks to the contents body of the directive.

.. availability:: Windows, Linux >= 3.17, not WASI   See :manpage:`python(1)` for more information

A consistent and parsable syntax will allow us to automatically generate a table of non-supported features on Emscripten and WASI later.