Check return result from Py_InitModule*().  This API can fail.

Probably should be backported.
diff --git a/Python/import.c b/Python/import.c
index f284ff4..8bd25f7 100644
--- a/Python/import.c
+++ b/Python/import.c
@@ -2817,6 +2817,8 @@
 
 	m = Py_InitModule4("imp", imp_methods, doc_imp,
 			   NULL, PYTHON_API_VERSION);
+	if (m == NULL)
+		goto failure;
 	d = PyModule_GetDict(m);
 
 	if (setint(d, "SEARCH_ERROR", SEARCH_ERROR) < 0) goto failure;
diff --git a/Python/marshal.c b/Python/marshal.c
index ff8247c..5617226 100644
--- a/Python/marshal.c
+++ b/Python/marshal.c
@@ -1107,5 +1107,7 @@
 PyMarshal_Init(void)
 {
 	PyObject *mod = Py_InitModule("marshal", marshal_methods);
+	if (mod == NULL)
+		return;
 	PyModule_AddIntConstant(mod, "version", Py_MARSHAL_VERSION);
 }
diff --git a/Python/sysmodule.c b/Python/sysmodule.c
index 5bbe950..f793b99 100644
--- a/Python/sysmodule.c
+++ b/Python/sysmodule.c
@@ -1027,6 +1027,8 @@
 #endif
 
 	m = Py_InitModule3("sys", sys_methods, sys_doc);
+	if (m == NULL)
+		return NULL;
 	sysdict = PyModule_GetDict(m);
 
 	{