Issue #18408: Fix _Py_DisplaySourceLine()

Report _Py_FindSourceFile() error, so the error is cleared;
and clear io.open(filename) exception on failure.

Python/traceback.c

@@ -246,10 +246,12 @@ _Py_DisplaySourceLine(PyObject *f, PyObject *filename, int lineno, int indent)
     binary = _PyObject_CallMethodId(io, &PyId_open, "Os", filename, "rb");
 
     if (binary == NULL) {
+        PyErr_Clear();
+
         binary = _Py_FindSourceFile(filename, buf, sizeof(buf), io);
         if (binary == NULL) {
             Py_DECREF(io);
-            return 0;
+            return -1;
         }
     }