Fixed out-of-bounce write to rawmode buffer. The fixed size buffer wasn't enlarged for the new 'x' flag. The buffer may contain the 5 flags xrwa+ and the \0 byte
diff --git a/Modules/_io/_iomodule.c b/Modules/_io/_iomodule.c
index 15781ac..0622c58 100644
--- a/Modules/_io/_iomodule.c
+++ b/Modules/_io/_iomodule.c
@@ -229,7 +229,7 @@
int creating = 0, reading = 0, writing = 0, appending = 0, updating = 0;
int text = 0, binary = 0, universal = 0;
- char rawmode[5], *m;
+ char rawmode[6], *m;
int line_buffering, isatty;
PyObject *raw, *modeobj = NULL, *buffer = NULL, *wrapper = NULL;