Port rev 55353 from Guido:
Add what looks like a necessary call to PyErr_NoMemory() when PyMem_MALLOC()
fails.

Will backport.
diff --git a/Objects/intobject.c b/Objects/intobject.c
index 9333a55..f72aea0 100644
--- a/Objects/intobject.c
+++ b/Objects/intobject.c
@@ -393,7 +393,7 @@
 	char *buffer = (char *)PyMem_MALLOC(length+1);
 
 	if (buffer == NULL)
-		return NULL;
+		return PyErr_NoMemory();
 
 	if (PyUnicode_EncodeDecimal(s, length, buffer, NULL)) {
 		PyMem_FREE(buffer);