Only set error string when dict lookup found no matching key (was setting

it for all failures, potentially masking other exceptions).

diff --git a/Modules/_csv.c b/Modules/_csv.c
index 7eb1e2275f9a27fd1e7c4c1580de4f07a28d1685..9f715e41d6b3b4516052aa73c787e68236bc795d 100644 (file)
--- a/Modules/_csv.c
+++ b/Modules/_csv.c
@@ -127,9 +127,12 @@ get_dialect_from_registry(PyObject * name_obj)
         PyObject *dialect_obj;
 
         dialect_obj = PyDict_GetItem(dialects, name_obj);
-        if (dialect_obj == NULL)
-            return PyErr_Format(error_obj, "unknown dialect");
-        Py_INCREF(dialect_obj);
+       if (dialect_obj == NULL) {
+               if (!PyErr_Occurred())
+                       PyErr_Format(error_obj, "unknown dialect");
+       }
+       else
+               Py_INCREF(dialect_obj);
         return dialect_obj;
 }