Fix rendering tracebacks with exceptions with a broken __getattr__

Lib/test/test_traceback.py

@@ -2209,6 +2209,18 @@ def __repr__(self):
         err_msg = "b'please do not show me as numbers'"
         self.assertEqual(self.get_report(e), vanilla + err_msg + '\n')
 
+        # an exception with a broken __getattr__ raising a non expected error
+        class BrokenException(Exception):
+            broken = False
+            def __getattr__(self, name):
+                if self.broken:
+                    raise ValueError(f'no {name}')
+
+        e = BrokenException(123)
+        vanilla = self.get_report(e)
+        e.broken = True
+        self.assertEqual(self.get_report(e), vanilla)
+
     def test_exception_with_multiple_notes(self):
         for e in [ValueError(42), SyntaxError('bad syntax')]:
             with self.subTest(e=e):

Lib/traceback.py

@@ -1051,7 +1051,12 @@ def __init__(self, exc_type, exc_value, exc_traceback, *, limit=None,
         # Capture now to permit freeing resources: only complication is in the
         # unofficial API _format_final_exc_line
         self._str = _safe_string(exc_value, 'exception')
-        self.__notes__ = getattr(exc_value, '__notes__', None)
+        notes = None
+        try:
+            notes = getattr(exc_value, '__notes__', None)
+        except Exception:
+            pass
+        self.__notes__ = notes
 
         self._is_syntax_error = False
         self._have_exc_type = exc_type is not None