pythongh-111609: Test end_offset in SyntaxError subclass (python#127830)

Test `end_offset` in SyntaxError subclass

Author: nineteendo

Lib/test/test_exceptions.py

@@ -2274,6 +2274,21 @@ def test_range_of_offsets(self):
                     self.assertIn(expected, err.getvalue())
                     the_exception = exc
 
+    def test_subclass(self):
+        class MySyntaxError(SyntaxError):
+            pass
+
+        try:
+            raise MySyntaxError("bad bad", ("bad.py", 1, 2, "abcdefg", 1, 7))
+        except SyntaxError as exc:
+            with support.captured_stderr() as err:
+                sys.__excepthook__(*sys.exc_info())
+            self.assertIn("""
+  File "bad.py", line 1
+    abcdefg
+     ^^^^^
+""", err.getvalue())
+
     def test_encodings(self):
         self.addCleanup(unlink, TESTFN)
         source = (