Document the surprising sideeffect PyErr_Print(). (GH-12081)

Did you know an API documented as printing the pending traceback would sometimes exit the process?

You do now.
(cherry picked from commit 4173772031747a9b249be4100b4aa9eda805ea23)

Co-authored-by: Gregory P. Smith <greg@krypto.org>

diff --git a/Doc/c-api/exceptions.rst b/Doc/c-api/exceptions.rst
index db302d8ee0ca4984933d2283feec1b981a65b33d..281e4c8473fd24c735448efb9d0e2a3d1fed8e1f 100644 (file)
--- a/Doc/c-api/exceptions.rst
+++ b/Doc/c-api/exceptions.rst
@@ -44,8 +44,12 @@ is a separate error indicator for each thread.
 .. c:function:: void PyErr_PrintEx(int set_sys_last_vars)
 
    Print a standard traceback to ``sys.stderr`` and clear the error indicator.
-   Call this function only when the error indicator is set.  (Otherwise it will
-   cause a fatal error!)
+   **Unless** the error is a ``SystemExit``.  In that case the no traceback
+   is printed and Python process will exit with the error code specified by
+   the ``SystemExit`` instance.
+
+   Call this function **only** when the error indicator is set.  Otherwise it
+   will cause a fatal error!
 
    If *set_sys_last_vars* is nonzero, the variables :data:`sys.last_type`,
    :data:`sys.last_value` and :data:`sys.last_traceback` will be set to the