Use PyImport_ImportModuleLevel() instead of PyImport_Import() for descriptor_pb2. PyImport_ImportModuleLevel() custom globals and locals pointing to some namespace we control, not normal-looking __builtins__

Change PYUPB_DESCRIPTOR_MODULE to "google.protobuf.descriptor_pb2" because protobuf python is using google.protobuf.descriptor_pb2 everywhere

Also check import result of PYUPB_DESCRIPTOR_MODULE

PiperOrigin-RevId: 565409795

upb/python/descriptor.c

@@ -112,7 +112,9 @@ static PyObject* PyUpb_DescriptorBase_GetOptions(PyUpb_DescriptorBase* self,
   if (!self->options) {
     // Load descriptors protos if they are not loaded already. We have to do
     // this lazily, otherwise, it would lead to circular imports.
-    PyObject* mod = PyImport_ImportModule(PYUPB_DESCRIPTOR_MODULE);
+    PyObject* mod = PyImport_ImportModuleLevel(PYUPB_DESCRIPTOR_MODULE, NULL,
+                                               NULL, NULL, 0);
+    if (mod == NULL) return NULL;
     Py_DECREF(mod);
 
     // Find the correct options message.

upb/python/protobuf.h

@@ -41,7 +41,6 @@
 #define PYUPB_PROTOBUF_PUBLIC_PACKAGE "google.protobuf"
 #define PYUPB_PROTOBUF_INTERNAL_PACKAGE "google.protobuf.internal"
 #define PYUPB_DESCRIPTOR_PROTO_PACKAGE "google.protobuf"
-#define PYUPB_DESCRIPTOR_MODULE "google.protobuf.descriptor_pb2"
 #define PYUPB_MODULE_NAME "google._upb._message"
 // end:github_only
 
@@ -49,10 +48,10 @@
 // #define PYUPB_PROTOBUF_PUBLIC_PACKAGE "google3.net.proto2.python.public"
 // #define PYUPB_PROTOBUF_INTERNAL_PACKAGE "google3.net.proto2.python.internal"
 // #define PYUPB_DESCRIPTOR_PROTO_PACKAGE "proto2"
-// #define PYUPB_DESCRIPTOR_MODULE "google3.net.proto2.proto.descriptor_pb2"
 // #define PYUPB_MODULE_NAME "google3.third_party.upb.python._message"
 // end:google_only
 
+#define PYUPB_DESCRIPTOR_MODULE "google.protobuf.descriptor_pb2"
 #define PYUPB_RETURN_OOM return PyErr_SetNone(PyExc_MemoryError), NULL
 
 struct PyUpb_WeakMap;