Fix warn_invalid_escape_sequence()

Issue #28691: Fix warn_invalid_escape_sequence(): handle correctly
DeprecationWarning raised as an exception. First clear the current exception to
replace the DeprecationWarning exception with a SyntaxError exception.

Unit test written by Serhiy Storchaka.

1 files changed, 7 insertions, 1 deletions

diff --git a/Python/ast.c b/Python/ast.c
index bfae6ed..14bcdb1 100644
--- a/Python/ast.c
+++ b/Python/ast.c
@@ -4129,7 +4129,13 @@ warn_invalid_escape_sequence(struct compiling *c, const node *n,
                                    NULL, NULL) < 0 &&
         PyErr_ExceptionMatches(PyExc_DeprecationWarning))
     {
-        const char *s = PyUnicode_AsUTF8(msg);
+        const char *s;
+
+        /* Replace the DeprecationWarning exception with a SyntaxError
+           to get a more accurate error report */
+        PyErr_Clear();
+
+        s = PyUnicode_AsUTF8(msg);
         if (s != NULL) {
             ast_error(c, n, s);
         }