Error 500 after disallowing unregistered users to browse

[Eduardo Rey Jara]

Hello all,

I deployed a course a couple months ago, it has been running all ok without errors but, today, after I have clicked "Allow unregistered Users to Browse Course" to make some changes, app engine has been giving to me this error 500:

1. 155.54.7.237 - umu.mooc [16/Nov/2015:00:04:43 -0800] "GET /cultura_italiana/dashboard HTTP/1.1" 500 225 - "Mozilla/5.0 (Windows NT 6.1; WOW64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/46.0.2490.86 Safari/537.36" "umu-mooc.appspot.com" ms=121 cpu_ms=38 cpm_usd=0.000025 app_engine_release=1.9.29 instance=00c61b117ce0a06551c7477f8e79406e38f8f967

2. E2015-11-16 09:04:43.863

   No JSON object could be decoded
   Traceback (most recent call last):
     File "/base/data/home/runtimes/python27/python27_lib/versions/third_party/webapp2-2.5.2/webapp2.py", line 1535, in __call__
       rv = self.handle_exception(request, response, e)
     File "/base/data/home/runtimes/python27/python27_lib/versions/third_party/webapp2-2.5.2/webapp2.py", line 1529, in __call__
       rv = self.router.dispatch(request, response)
     File "/base/data/home/runtimes/python27/python27_lib/versions/third_party/webapp2-2.5.2/webapp2.py", line 1278, in default_dispatcher
       return route.handler_adapter(request, response)
     File "/base/data/home/runtimes/python27/python27_lib/versions/third_party/webapp2-2.5.2/webapp2.py", line 1102, in __call__
       return handler.dispatch()
     File "/base/data/home/apps/s~umu-mooc/1.382271662011287848/controllers/sites.py", line 1169, in dispatch
       super(ApplicationRequestHandler, self).dispatch()
     File "/base/data/home/runtimes/python27/python27_lib/versions/third_party/webapp2-2.5.2/webapp2.py", line 572, in dispatch
       return self.handle_exception(e, self.app.debug)
     File "/base/data/home/runtimes/python27/python27_lib/versions/third_party/webapp2-2.5.2/webapp2.py", line 570, in dispatch
       return method(*args, **kwargs)
     File "/base/data/home/apps/s~umu-mooc/1.382271662011287848/controllers/sites.py", line 1337, in get
       self.invoke_http_verb('GET', path, self._login_or_404)
     File "/base/data/home/apps/s~umu-mooc/1.382271662011287848/controllers/sites.py", line 1318, in invoke_http_verb
       getattr(handler, verb.lower())()
     File "/base/data/home/apps/s~umu-mooc/1.382271662011287848/modules/dashboard/dashboard.py", line 197, in get
       return super(DashboardHandler, self).get()
     File "/base/data/home/apps/s~umu-mooc/1.382271662011287848/controllers/utils.py", line 182, in get
       return handler()
     File "/base/data/home/apps/s~umu-mooc/1.382271662011287848/modules/dashboard/dashboard.py", line 552, in get_outline
       course_info.append('Schema Version: %s' % courses.Course(self).version)
     File "/base/data/home/apps/s~umu-mooc/1.382271662011287848/models/courses.py", line 2510, in __init__
       self._model = self._load(self._app_context)
     File "/base/data/home/apps/s~umu-mooc/1.382271662011287848/models/courses.py", line 2436, in _load
       model = CourseModel13.load(app_context)
     File "/base/data/home/apps/s~umu-mooc/1.382271662011287848/models/courses.py", line 973, in load
       course = PersistentCourse13.load(app_context)
     File "/base/data/home/apps/s~umu-mooc/1.382271662011287848/models/courses.py", line 902, in load
       persistent.deserialize(stream.read())
     File "/base/data/home/apps/s~umu-mooc/1.382271662011287848/models/courses.py", line 917, in deserialize
       adict = transforms.loads(json_text)
     File "/base/data/home/apps/s~umu-mooc/1.382271662011287848/models/transforms.py", line 152, in loads
       return json.loads(s, **kwargs)
     File "/base/data/home/runtimes/python27/python27_dist/lib/python2.7/json/__init__.py", line 338, in loads
       return _default_decoder.decode(s)
     File "/base/data/home/runtimes/python27/python27_dist/lib/python2.7/json/decoder.py", line 365, in decode
       obj, end = self.raw_decode(s, idx=_w(s, 0).end())
     File "/base/data/home/runtimes/python27/python27_dist/lib/python2.7/json/decoder.py", line 383, in raw_decode
       raise ValueError("No JSON object could be decoded")
   ValueError: No JSON object could be decoded

I have no idea what I've done wrong and how to fix it. Anyone can tell me something about this error? We have deployed 1.9.29 version. Anyway, we have 2 courses more and they are still running ok.