Restore GIL in nis_cat in case of error.

Misc/NEWS

@@ -57,6 +57,8 @@ Core and Builtins
 Extensions
 ----------
 
+- Restore GIL in nis_cat in case of error.
+
 - Issue #665761: ``functools.reduce()`` will no longer mask exceptions
   other than ``TypeError`` raised by the iterator argument.
 

Modules/nismodule.c

@@ -124,6 +124,7 @@ nis_foreach (int instatus, char *inkey, int inkeylen, char *inval,
             PyErr_Clear();
             Py_XDECREF(key);
             Py_XDECREF(val);
+            indata->state = PyEval_SaveThread();
             return 1;
         }
         err = PyDict_SetItem(indata->dict, key, val);