Check for errors in creating sub-interpreters when testing the C API.
diff --git a/Modules/_testcapimodule.c b/Modules/_testcapimodule.c
index b00ac20..bcb3a0f 100644
--- a/Modules/_testcapimodule.c
+++ b/Modules/_testcapimodule.c
@@ -2396,6 +2396,14 @@
PyThreadState_Swap(NULL);
substate = Py_NewInterpreter();
+ if (substate == NULL) {
+ /* Since no new thread state was created, there is no exception to
+ propagate; raise a fresh one after swapping in the old thread
+ state. */
+ PyThreadState_Swap(mainstate);
+ PyErr_SetString(PyExc_RuntimeError, "sub-interpreter creation failed");
+ return NULL;
+ }
r = PyRun_SimpleString(code);
Py_EndInterpreter(substate);