Allow RuntimeError on older Python

Python < 3.12 wraps errors in __set_name__ in a RuntimeError. I've updated the test accordingly.
We now test that either the exception is the
expected one, or that the expected exception
is the direct cause.

Author: rwb27

tests/test_properties.py

@@ -71,22 +71,30 @@ class BasicThing(Thing):
     assert issubclass(BasicThing.prop.model, BaseModel)
 
 
+def exception_is_or_is_caused_by(err: Exception, cls: type[Exception]):
+    return isinstance(err, cls) or isinstance(err.__cause__, cls)
+
+
 def test_instantiation_with_type_and_model():
     """If a model is specified, we check it matches the inferred type."""
 
     class BasicThing(Thing):
         prop = ThingProperty[bool](model=bool, initial_value=False)
 
-    with pytest.raises(MismatchedTypeError):
+    with pytest.raises(Exception) as e:
 
         class InvalidThing(Thing):
             prop = ThingProperty[bool](model=int, initial_value=False)
 
-    with pytest.raises(MissingTypeError):
+    assert exception_is_or_is_caused_by(e.value, MismatchedTypeError)
+
+    with pytest.raises(Exception) as e:
 
         class InvalidThing(Thing):
             prop = ThingProperty(model=bool, initial_value=False)
 
+    assert exception_is_or_is_caused_by(e.value, MissingTypeError)
+
 
 def test_missing_default():
     """Test that a default is required if no model is specified."""