Add support for Python 3.13

Start testing on 3.13, and fix a test for the change introduced in
python/cpython#103232.

.circleci/config.yml

@@ -37,6 +37,7 @@ common: &common
               - cimg/python:3.10
               - cimg/python:3.11
               - cimg/python:3.12
+              - cimg/python:3.13
     - python/pip-run-tests:
         name: mock-backport
         image: cimg/python:3.11

testfixtures/compat.py

@@ -8,3 +8,4 @@
 PY_310_PLUS: bool = PY_VERSION >= (3, 10)
 PY_311_PLUS: bool = PY_VERSION >= (3, 11)
 PY_312_PLUS: bool = PY_VERSION >= (3, 12)
+PY_313_PLUS: bool = PY_VERSION >= (3, 13)

testfixtures/tests/test_replace.py

@@ -21,7 +21,7 @@
 from testfixtures.tests import sample2
 from .sample1 import z, X
 from .sample3 import SOME_CONSTANT
-from ..compat import PY_310_PLUS
+from ..compat import PY_310_PLUS, PY_313_PLUS
 
 from warnings import catch_warnings
 
@@ -1362,7 +1362,10 @@ def test_invalid_attribute_on_instance_of_slotted_class(self):
         obj = OriginE()
         assert not hasattr(obj, '__dict__')
         replace_ = Replacer()
-        with ShouldRaise(AttributeError("'OriginE' object has no attribute 'bad'")):
+        message = "'OriginE' object has no attribute 'bad'"
+        if PY_313_PLUS:
+            message += " and no __dict__ for setting new attributes"
+        with ShouldRaise(AttributeError(message)):
             replace_(obj, name='bad', replacement=42, strict=self.strict)
 
     def test_method_on_instance_of_slotted_subclass(self):