fix scope of closures that was missing a 'directives' dict, explicitly mark closure classes 'final'

Cython/Compiler/ParseTreeTransforms.py

@@ -1293,6 +1293,7 @@ class CreateClosureClasses(CythonTransform):
         func_scope.scope_class = entry
         class_scope = entry.type.scope
         class_scope.is_internal = True
+        class_scope.directives = {'final': True}
         if node.entry.scope.is_closure_scope:
             class_scope.declare_var(pos=node.pos,
                                     name=Naming.outer_scope_cname, # this could conflict?