acme.messages.Error: add mutability (#9546)

* acme.messages.Error: add mutability

As of Python 3.11, an exception caught within a `with` statement will
update the __traceback__ attribute. Because acme.messages.Error was
immutable, this was causing a knock-on exception, causing certbot to
exit abnormally. This commit hacks in mutability for acme.messages.Error

Fixes #9539

* Add CHANGELOG entry

acme/acme/messages.py

@@ -123,6 +123,9 @@ class Error(jose.JSONObjectWithFields, errors.Error):
 
     https://datatracker.ietf.org/doc/html/rfc7807
 
+    Note: Although Error inherits from JSONObjectWithFields, which is immutable,
+    we add mutability for Error to comply with the Python exception API.
+
     :ivar str typ:
     :ivar str title:
     :ivar str detail:
@@ -185,6 +188,10 @@ class Error(jose.JSONObjectWithFields, errors.Error):
             return code
         return None
 
+    # Hack to allow mutability on Errors (see GH #9539)
+    def __setattr__(self, name: str, value: Any) -> None:
+        return object.__setattr__(self, name, value)
+
     def __str__(self) -> str:
         result = b' :: '.join(
             part.encode('ascii', 'backslashreplace') for part in

acme/tests/messages_test.py

@@ -1,6 +1,7 @@
 """Tests for acme.messages."""
 from typing import Dict
 import unittest
+import contextlib
 from unittest import mock
 import warnings
 
@@ -91,6 +92,22 @@ class ErrorTest(unittest.TestCase):
             u"Problem for {1.identifier.value}: {1.typ} :: {1.description} :: {1.detail} :: {1.title}").format(
         self.error_with_subproblems, self.subproblem))
 
+    # this test is based on a minimal reproduction of a contextmanager/immutable
+    # exception related error: https://github.com/python/cpython/issues/99856
+    def test_with_context_manager(self):
+        from acme.messages import Error
+
+        @contextlib.contextmanager
+        def context():
+            yield
+
+        try:
+            with context():
+                raise self.error_custom
+        except Error as e:
+            self.assertIsNotNone(self.error_custom.__traceback__)
+
+
 class ConstantTest(unittest.TestCase):
     """Tests for acme.messages._Constant."""
 

certbot/CHANGELOG.md

@@ -17,7 +17,7 @@ Certbot adheres to [Semantic Versioning](https://semver.org/).
 
 ### Fixed
 
-*
+* Fixed a bug where Certbot would crash with `AttributeError: can't set attribute` on ACME server errors in Python 3.11. See [GH #9539](https://github.com/certbot/certbot/issues/9539).
 
 More details about these changes can be found on our GitHub repo.