Set interp-_ready on the main interpreter.

Author: ericsnowcurrently

Python/pylifecycle.c

@@ -477,6 +477,7 @@ pyinit_core_reconfigure(_PyRuntimeState *runtime,
     if (interp == NULL) {
         return _PyStatus_ERR("can't make main interpreter");
     }
+    assert(interp->_ready);
 
     status = _PyConfig_Write(config, runtime);
     if (_PyStatus_EXCEPTION(status)) {
@@ -632,6 +633,7 @@ pycore_create_interpreter(_PyRuntimeState *runtime,
     assert(interp != NULL);
     assert(_Py_IsMainInterpreter(interp));
     _PyInterpreterState_SetWhence(interp, _PyInterpreterState_WHENCE_RUNTIME);
+    interp->_ready = 1;
 
     status = _PyConfig_Copy(&interp->config, src_config);
     if (_PyStatus_EXCEPTION(status)) {