Fix crasher for when an object's __del__ creates a new weakref to itself.
Patch only fixes new-style classes; classic classes still buggy.

Closes bug #1377858.  Already backported.
diff --git a/Misc/NEWS b/Misc/NEWS
index 65b0672..ad72b08 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -12,6 +12,10 @@
 Core and builtins
 -----------------
 
+- Bug #1377858: Fix the segfaulting of the interpreter when an object created
+  a weakref on itself during a __del__ call for new-style classes (classic
+  classes still have the bug).
+
 - Bug #1579370: Make PyTraceBack_Here use the current thread, not the
   frame's thread state.