bpo-44335: Fix a regression when identifying invalid characters in syntax errors (GH-26589)

(cherry picked from commit d334c73b56756e90c33ce06e3a6ec23271aa099d)

Co-authored-by: Pablo Galindo <Pablogsal@gmail.com>
diff --git a/Lib/test/test_exceptions.py b/Lib/test/test_exceptions.py
index 5fb651f..df5778d 100644
--- a/Lib/test/test_exceptions.py
+++ b/Lib/test/test_exceptions.py
@@ -211,6 +211,7 @@ def testSyntaxErrorOffset(self):
         check('lambda x: x = 2', 1, 1)
         check('f{a + b + c}', 1, 2)
         check('[file for str(file) in []\n])', 2, 2)
+        check('a = « hello » « world »', 1, 5)
         check('[\nfile\nfor str(file)\nin\n[]\n]', 3, 5)
         check('[file for\n str(file) in []]', 2, 2)
         check("ages = {'Alice'=22, 'Bob'=23}", 1, 16)