allow weakref to TransactionContext classes

diff --git a/lib/sqlalchemy/engine/util.py b/lib/sqlalchemy/engine/util.py
index 6aadd5c5fe169f1964d17626eebcb848d9ce6193..32b59e8e604c685e15c16d022e33e3b1c8be99d9 100644 (file)
--- a/lib/sqlalchemy/engine/util.py
+++ b/lib/sqlalchemy/engine/util.py
@@ -43,7 +43,7 @@ class TransactionalContext:
 
     """
 
-    __slots__ = ("_outer_trans_ctx", "_trans_subject")
+    __slots__ = ("_outer_trans_ctx", "_trans_subject", "__weakref__")
 
     def _transaction_is_active(self):
         raise NotImplementedError()