1 files changed, 22 insertions, 0 deletions
diff --git a/lib/sqlalchemy/sql/base.py b/lib/sqlalchemy/sql/base.py
index 6cdab8eac..4bc6d8280 100644
--- a/lib/sqlalchemy/sql/base.py
+++ b/lib/sqlalchemy/sql/base.py
@@ -1388,3 +1388,25 @@ def _bind_or_error(schemaitem, msg=None):
             )
         raise exc.UnboundExecutionError(msg)
     return bind
+
+
+def _entity_namespace_key(entity, key):
+    """Return an entry from an entity_namespace.
+
+
+    Raises :class:`_exc.InvalidRequestError` rather than attribute error
+    on not found.
+
+    """
+
+    ns = entity.entity_namespace
+    try:
+        return getattr(ns, key)
+    except AttributeError as err:
+        util.raise_(
+            exc.InvalidRequestError(
+                'Entity namespace for "%s" has no property "%s"'
+                % (entity, key)
+            ),
+            replace_context=err,
+        )