PicklingError caused by None session on submit

Hello everyone,
Thank you for reading this !
I am a 3 weeks newbie in django. I occurred a picklingerror when integrating qrcode payment(wechat payment) with django-oscar.
Steps cause the promblem:

1. Add a product in basket and chose to pay directly;
2. Chose payment method;
3. Jump to preview page and press the "place order" button on it(which by normally will jump to scan code page which has a qrcode on it);

Error message:
it works well before, but since tomorrow it display picklingerror like this:

PicklingError at /zh-cn/checkout/preview/
Can't pickle <type 'function'>: attribute lookup __builtin__.function failed

Traceback:

Environment:
Request Method: POST
Request URL: http://xiwen.proxy.qqbrowser.cc:8000/zh-cn/checkout/preview/

Django Version: 1.8.5
Python Version: 2.7.10
Installed Applications:
['django.contrib.auth',
 'django.contrib.contenttypes',
 'django.contrib.sessions',
 'django.contrib.sites',
 'django.contrib.messages',
 'django.contrib.admin',
 'django.contrib.flatpages',
 'django.contrib.staticfiles',
 'django.contrib.sitemaps',
 'django_extensions',
 'debug_toolbar',
 'apps.gateway',
 'widget_tweaks',
 'wcpay',
 'oscar',
 'oscar.apps.analytics',
 'apps.checkout',
 'oscar.apps.address',
 'oscar.apps.shipping',
 'oscar.apps.catalogue',
 'oscar.apps.catalogue.reviews',
 'oscar.apps.partner',
 'oscar.apps.basket',
 'oscar.apps.payment',
 'oscar.apps.offer',
 'oscar.apps.order',
 'oscar.apps.customer',
 'oscar.apps.promotions',
 'oscar.apps.search',
 'oscar.apps.voucher',
 'oscar.apps.wishlists',
 'oscar.apps.dashboard',
 'oscar.apps.dashboard.reports',
 'oscar.apps.dashboard.users',
 'oscar.apps.dashboard.orders',
 'oscar.apps.dashboard.promotions',
 'oscar.apps.dashboard.catalogue',
 'oscar.apps.dashboard.offers',
 'oscar.apps.dashboard.partners',
 'oscar.apps.dashboard.pages',
 'oscar.apps.dashboard.ranges',
 'oscar.apps.dashboard.reviews',
 'oscar.apps.dashboard.vouchers',
 'oscar.apps.dashboard.communications',
 'oscar.apps.dashboard.shipping',
 'haystack',
 'treebeard',
 'sorl.thumbnail',
 'django_tables2']
Installed Middleware:
('django.contrib.sessions.middleware.SessionMiddleware',
 'django.contrib.auth.middleware.AuthenticationMiddleware',
 'django.contrib.messages.middleware.MessageMiddleware',
 'django.contrib.flatpages.middleware.FlatpageFallbackMiddleware',
 'django.middleware.locale.LocaleMiddleware',
 'django.middleware.common.CommonMiddleware',
 'oscar.apps.basket.middleware.BasketMiddleware')


Traceback:
File "/Library/Python/2.7/site-packages/django/core/handlers/base.py" in get_response
  223.                 response = middleware_method(request, response)
File "/Library/Python/2.7/site-packages/django/contrib/sessions/middleware.py" in process_response
  50.                         request.session.save()
File "/Library/Python/2.7/site-packages/django/contrib/sessions/backends/db.py" in save
  59.             session_data=self.encode(self._get_session(no_load=must_create)),
File "/Library/Python/2.7/site-packages/django/contrib/sessions/backends/base.py" in encode
  88.         serialized = self.serializer().dumps(session_dict)
File "/Library/Python/2.7/site-packages/django/contrib/sessions/serializers.py" in dumps
  15.         return pickle.dumps(obj, pickle.HIGHEST_PROTOCOL)

Exception Type: PicklingError at /zh-cn/checkout/preview/
Exception Value: Can't pickle <type 'function'>: attribute lookup __builtin__.function failed

Debug info:
i debugged and found this problem is threw from handler/base.py.
By the way, i didn't remember i have change any code which cause this problem.

try:
            # Apply response middleware, regardless of the response          
 for middleware_method in self._response_middleware:
                response = middleware_method(request, response)
                # Complain if the response middleware returned None (a common error).
                if response is None:
                    raise ValueError(
                        "%s.process_response didn't return an "
                        "HttpResponse object. It returned None instead."
                        % (middleware_method.__self__.__class__.__name__))
            response = self.apply_response_fixes(request, response)
        except:  # Any exception should be gathered and handled
            signals.got_request_exception.send(sender=self.__class__, request=request)
            response = self.handle_uncaught_exception(request, resolver, sys.exc_info())

Part of my code:

• mysite/app/checkout/views.py

class MultiPaymentDetailsView(RedirectSessionMixin, OscarPaymentDetailsView):
    template_name = 'checkout/payment_details.html'
    template_name_preview = 'checkout/preview.html'
    paymentsource_name={
        'WeChatPay':"微信担保",
        }
    paymentsource_method={
        'WeChatPay':WechatpayHandle
    }

    def get_context_data(self, **kwargs):
        context=super(OscarPaymentDetailsView,self).get_context_data(**kwargs)
        context['paymethod']=self.paymentsource_name[self.get_paymethod()]
        return context

    def get(self, request, *args, **kwargs):
        if kwargs.get('paymethod'):
            self.save_paymethod(kwargs.get('paymethod'))
            return HttpResponseRedirect('/checkout/preview')
        return super(OscarPaymentDetailsView,self).get(self,request, *args, **kwargs)


    def handle_payment(self, order_number, total, **kwargs):
        """
        Make submission to scancode
        """
        self.set_order_number(order_number)
        self.set_info()
        paymethod=self.paymentsource_method[self.get_paymethod()]
        paymethod(self,order_number, **kwargs)

• mysite/wcpay/views.py

def WechatpayHandle(paymentview,order_number, **kwargs):
    """
    Make submission to Wechat
    """
    wechatpaymon=WechatpaySessionMixin(paymentview.checkout_session)
    if settings.DEBUG:
        base_url = 'http://%s' % paymentview.request.META['HTTP_HOST']
    else:
        base_url = 'https://%s' % Site.objects.get_current().domain

    # 向微信服务器发送统一下单请求｜send place order request to weixin server
    # notify_url = 'http://8d9ce024.ngrok.io/zh-cn/checkout/wechatpay/respond'
    notify_url = "%s%s" % (base_url, reverse("checkout:wcpay:wechat-respond"))
    print 'notify_url: ',notify_url
    comm = Common_util_pub()
    out_trade_no = '{0}{1}{2}'.format('scan','_',int(time.time()))
    out_trade_no = '{0}{1}'.format(out_trade_no,comm.createNoncestr(32 - len(out_trade_no)))
    unifiedpay = UnifiedOrder_pub()
    unifiedpay.setParameter('out_trade_no', out_trade_no)
    unifiedpay.setParameter('body', '扫一扫支付')
    unifiedpay.setParameter('total_fee', '1')
    unifiedpay.setParameter('notify_url', notify_url)
    unifiedpay.setParameter('trade_type', 'NATIVE')
    unifiedorder = unifiedpay.getPrepayId()

    start_pay_url = '/zh-cn/checkout/wechatpay/scancode'
    code_url = unifiedorder.get('code_url')
    # start_pay_url = '/checkout/wechatpay/scancode'
    # rp = requests.post(start_pay_url1, json.dumps(code_url))
    # print rp
    start_pay_url = start_pay_url + '/?code_url=' + code_url
    # wechatpaymon.set_wechatpay()
    raise RedirectRequired(start_pay_url)

Reference:
https://github.com/amyhoo/django-oscar-alipay
a good project which didn't implement qrcode scan but quite the same way.

Any ideas about this problem or materials about how to develop qrcode payment with django will be grateful !
 


Thanks!
Xiwen

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