fix iterator in testsuite helpers

flask/testsuite/helpers.py

@@ -15,7 +15,7 @@ import unittest
 from logging import StreamHandler
 from flask.testsuite import FlaskTestCase, catch_warnings, catch_stderr
 from werkzeug.http import parse_cache_control_header, parse_options_header
-from flask._compat import StringIO, text_type
+from flask._compat import StringIO, text_type, implements_iterator
 
 
 def has_encoding(name):
@@ -485,6 +485,7 @@ class StreamingTestCase(FlaskTestCase):
         app = flask.Flask(__name__)
         app.testing = True
         called = []
+        @implements_iterator
         class Wrapper(object):
             def __init__(self, gen):
                 self._gen = gen
@@ -492,7 +493,7 @@ class StreamingTestCase(FlaskTestCase):
                 return self
             def close(self):
                 called.append(42)
-            def next(self):
+            def __next__(self):
                 return next(self._gen)
         @app.route('/')
         def index():