Use generator utility code inside GeneratorDefNode instead of YieldExprNode

Cython/Compiler/ExprNodes.py

@@ -5253,7 +5253,6 @@ class YieldExprNode(ExprNode):
             self.arg.analyse_types(env)
             if not self.arg.type.is_pyobject:
                 self.arg = self.arg.coerce_to_pyobject(env)
-        env.use_utility_code(generator_utility_code)
 
     def generate_evaluation_code(self, code):
         self.label_name = code.new_label('resume_from_yield')

Cython/Compiler/Nodes.py

@@ -2989,6 +2989,9 @@ class GeneratorDefNode(DefNode):
         code.putln("return (PyObject *) %s;" % Naming.cur_scope_cname);
 
     def generate_function_definitions(self, env, code):
+        from ExprNodes import generator_utility_code
+        env.use_utility_code(generator_utility_code)
+
         self.gbody.generate_function_header(code, proto=True)
         super(GeneratorDefNode, self).generate_function_definitions(env, code)
         self.gbody.generate_function_definitions(env, code)