Mark signal.[Signals.]SIGSTOP as unavailable on Windows

[jonathandung]

Documentation

In the signal page hosted on the python docs, signal.SIGSTOP is not marked as Unix-only, unlike other signals that Windows lacks.

The signal functionality on Windows is much more limited than on Unix-like systems, famously only defining a few signals. Therefore, many signals are available on Unix only, which is reflected in the typeshed stubs and the documentation.

For example, in the .rst source:

.. data:: SIGPROF

   Profiling timer expired.

   .. availability:: Unix.

.. data:: SIGQUIT

   Terminal quit signal.

   .. availability:: Unix.

However, this is missing under SIGSTOP:

.. data:: SIGSTOP

   Stop executing (cannot be caught or ignored).

.. data:: SIGSTKFLT

   Stack fault on coprocessor. The Linux kernel does not raise this signal: it
   can only be raised in user space.

A pull request will be opened to fix this, if appropriate.

Linked PRs

• gh-146318: Document that signal.SIGSTOP is unix-only #146319