Issue #12149: Update the method cache after a type's dictionnary gets
cleared by the garbage collector.  This fixes a segfault when an instance
and its type get caught in a reference cycle, and the instance's
deallocator calls one of the methods on the type (e.g. when subclassing
IOBase).

Diagnosis and patch by Davide Rizzo.
diff --git a/Misc/NEWS b/Misc/NEWS
index 9a46b72..3df8e95 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -10,6 +10,12 @@
 Core and Builtins
 -----------------
 
+- Issue #12149: Update the method cache after a type's dictionnary gets
+  cleared by the garbage collector.  This fixes a segfault when an instance
+  and its type get caught in a reference cycle, and the instance's
+  deallocator calls one of the methods on the type (e.g. when subclassing
+  IOBase).  Diagnosis and patch by Davide Rizzo.
+
 - Issue #9611, #9015: FileIO.read() clamps the length to INT_MAX on Windows.
 
 - When a generator yields, do not retain the caller's exception state on the