bpo-35370: PyEval_SetTrace() logs unraisable error (GH-18977) (GH-19029)

If PySys_Audit() fails in PyEval_SetProfile() or PyEval_SetTrace(),
log the error as an unraisable exception.

(cherry picked from commit f6a5850)

Author: vstinner

Misc/NEWS.d/next/C API/2020-03-13-16-44-23.bpo-35370.sXRA-r.rst

@@ -0,0 +1,2 @@
+If :c:func:`PySys_Audit` fails in :c:func:`PyEval_SetProfile` or
+:c:func:`PyEval_SetTrace`, log the error as an unraisable exception.

Python/ceval.c

@@ -4686,6 +4686,7 @@ void
 PyEval_SetProfile(Py_tracefunc func, PyObject *arg)
 {
     if (PySys_Audit("sys.setprofile", NULL) < 0) {
+        _PyErr_WriteUnraisableMsg("in PyEval_SetProfile", NULL);
         return;
     }
 
@@ -4707,6 +4708,7 @@ void
 PyEval_SetTrace(Py_tracefunc func, PyObject *arg)
 {
     if (PySys_Audit("sys.settrace", NULL) < 0) {
+        _PyErr_WriteUnraisableMsg("in PyEval_SetTrace", NULL);
         return;
     }