gh-100557: Clarify signal.pause() docs to explain it only wakes on handled signals

Doc/library/calendar.rst

@@ -580,8 +580,11 @@ The :mod:`!calendar` module defines the following exceptions:
 
 .. exception:: IllegalMonthError(month)
 
-   A subclass of :exc:`ValueError`,
+   A subclass of both :exc:`ValueError` and :exc:`IndexError`,
    raised when the given month number is outside of the range 1-12 (inclusive).
+   The :exc:`IndexError` base class is preserved for backwards compatibility
+   with code that caught :exc:`IndexError` for bad month numbers prior to
+   Python 3.13.
 
    .. attribute:: month
 

Misc/NEWS.d/next/Documentation/2026-04-17-02-28-55.gh-issue-148663.MHIbRB.rst

@@ -0,0 +1,5 @@
+Document that :class:`calendar.IllegalMonthError` inherits from both
+:exc:`ValueError` and :exc:`IndexError`, preserving :exc:`IndexError` for
+backwards compatibility with code that caught it for bad month numbers prior
+to Python 3.13.
+###########################################################################

Misc/NEWS.d/next/Documentation/2026-04-18-12-38-41.gh-issue-100557.a6MWvZ.rst

@@ -0,0 +1,4 @@
+Clarify the documentation for :func:`signal.pause` to explain that it only
+returns when a signal with an installed handler is delivered, not when an
+ignored signal arrives.
+###########################################################################

Modules/signalmodule.c

@@ -395,7 +395,11 @@ signal_alarm_impl(PyObject *module, int seconds)
 /*[clinic input]
 signal.pause
 
-Wait until a signal arrives.
+Wait until a signal with an installed handler is delivered.
+
+Cause the process to sleep until a signal is received that either
+terminates it or causes it to call a signal-catching function. If the
+signal is being ignored, pause() is not interrupted.
 [clinic start generated code]*/
 
 static PyObject *