catch nasty exception classes with __new__ that doesn't return a exception (closes #11627)

Patch from Andreas Stührk.
diff --git a/Misc/NEWS b/Misc/NEWS
index 18ee9d3..cba337a 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -10,6 +10,9 @@
 Core and Builtins
 -----------------
 
+- Issue #11627: Fix segfault when __new__ on a exception returns a non-exception
+  class.
+
 - 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