Reset student attempt results in error

[natea]

When I try to reset the student attempt using the staff debug tool, I get the following error:

2016-09-24 21:08:54,848 ERROR 13297 [root] exceptions.py:9 - Uncaught exception from <class 'django.core.handlers.wsgi.WSGIHandler'>
Traceback (most recent call last):
  File "/edx/app/edxapp/venvs/edxapp/local/lib/python2.7/site-packages/django/core/handlers/base.py", line 132, in get_response
    response = wrapped_callback(request, *callback_args, **callback_kwargs)
  File "/edx/app/edxapp/venvs/edxapp/local/lib/python2.7/site-packages/django/views/decorators/http.py", line 45, in inner
    return func(request, *args, **kwargs)
  File "/edx/app/edxapp/venvs/edxapp/local/lib/python2.7/site-packages/django/utils/decorators.py", line 110, in _wrapped_view
    response = view_func(request, *args, **kwargs)
  File "/edx/app/edxapp/venvs/edxapp/local/lib/python2.7/site-packages/django/views/decorators/cache.py", line 43, in _cache_controlled
    response = viewfunc(request, *args, **kw)
  File "/edx/app/edxapp/edx-platform/lms/djangoapps/instructor/views/api.py", line 201, in wrapped
    return func(*args, **kwargs)
  File "/edx/app/edxapp/edx-platform/lms/djangoapps/instructor/views/api.py", line 174, in wrapped
    return func(*args, **kwargs)
  File "/edx/app/edxapp/edx-platform/lms/djangoapps/instructor/views/api.py", line 125, in wrapped
    return func(request, *args, **kwargs)
  File "/edx/app/edxapp/edx-platform/lms/djangoapps/instructor/views/api.py", line 1984, in reset_student_attempts
    delete_module=delete_module
  File "/edx/app/edxapp/edx-platform/lms/djangoapps/instructor/enrollment.py", line 271, in reset_student_attempts
    _reset_module_attempts(module_to_reset)
  File "/edx/app/edxapp/edx-platform/lms/djangoapps/instructor/enrollment.py", line 281, in _reset_module_attempts
    problem_state = json.loads(studentmodule.state)
  File "/usr/lib/python2.7/json/__init__.py", line 338, in loads
    return _default_decoder.decode(s)
  File "/usr/lib/python2.7/json/decoder.py", line 366, in decode
    obj, end = self.raw_decode(s, idx=_w(s, 0).end())
TypeError: expected string or buffer
Internal Server Error: /courses/course-v1:edX+DemoX+Demo_Course/instructor/api/reset_student_attempts
Traceback (most recent call last):
  File "/edx/app/edxapp/venvs/edxapp/local/lib/python2.7/site-packages/django/core/handlers/base.py", line 132, in get_response
    response = wrapped_callback(request, *callback_args, **callback_kwargs)
  File "/edx/app/edxapp/venvs/edxapp/local/lib/python2.7/site-packages/django/views/decorators/http.py", line 45, in inner
    return func(request, *args, **kwargs)
  File "/edx/app/edxapp/venvs/edxapp/local/lib/python2.7/site-packages/django/utils/decorators.py", line 110, in _wrapped_view
    response = view_func(request, *args, **kwargs)
  File "/edx/app/edxapp/venvs/edxapp/local/lib/python2.7/site-packages/django/views/decorators/cache.py", line 43, in _cache_controlled
    response = viewfunc(request, *args, **kw)
  File "/edx/app/edxapp/edx-platform/lms/djangoapps/instructor/views/api.py", line 201, in wrapped
    return func(*args, **kwargs)
  File "/edx/app/edxapp/edx-platform/lms/djangoapps/instructor/views/api.py", line 174, in wrapped
    return func(*args, **kwargs)
  File "/edx/app/edxapp/edx-platform/lms/djangoapps/instructor/views/api.py", line 125, in wrapped
    return func(request, *args, **kwargs)
  File "/edx/app/edxapp/edx-platform/lms/djangoapps/instructor/views/api.py", line 1984, in reset_student_attempts
    delete_module=delete_module
  File "/edx/app/edxapp/edx-platform/lms/djangoapps/instructor/enrollment.py", line 271, in reset_student_attempts
    _reset_module_attempts(module_to_reset)
  File "/edx/app/edxapp/edx-platform/lms/djangoapps/instructor/enrollment.py", line 281, in _reset_module_attempts
    problem_state = json.loads(studentmodule.state)
  File "/usr/lib/python2.7/json/__init__.py", line 338, in loads
    return _default_decoder.decode(s)
  File "/usr/lib/python2.7/json/decoder.py", line 366, in decode
    obj, end = self.raw_decode(s, idx=_w(s, 0).end())
TypeError: expected string or buffer
2016-09-24 21:08:54,850 ERROR 13297 [django.request] base.py:256 - Internal Server Error: /courses/course-v1:edX+DemoX+Demo_Course/instructor/api/reset_student_attempts
Traceback (most recent call last):
  File "/edx/app/edxapp/venvs/edxapp/local/lib/python2.7/site-packages/django/core/handlers/base.py", line 132, in get_response
    response = wrapped_callback(request, *callback_args, **callback_kwargs)
  File "/edx/app/edxapp/venvs/edxapp/local/lib/python2.7/site-packages/django/views/decorators/http.py", line 45, in inner
    return func(request, *args, **kwargs)
  File "/edx/app/edxapp/venvs/edxapp/local/lib/python2.7/site-packages/django/utils/decorators.py", line 110, in _wrapped_view
    response = view_func(request, *args, **kwargs)
  File "/edx/app/edxapp/venvs/edxapp/local/lib/python2.7/site-packages/django/views/decorators/cache.py", line 43, in _cache_controlled
    response = viewfunc(request, *args, **kw)
  File "/edx/app/edxapp/edx-platform/lms/djangoapps/instructor/views/api.py", line 201, in wrapped
    return func(*args, **kwargs)
  File "/edx/app/edxapp/edx-platform/lms/djangoapps/instructor/views/api.py", line 174, in wrapped
    return func(*args, **kwargs)
  File "/edx/app/edxapp/edx-platform/lms/djangoapps/instructor/views/api.py", line 125, in wrapped
    return func(request, *args, **kwargs)
  File "/edx/app/edxapp/edx-platform/lms/djangoapps/instructor/views/api.py", line 1984, in reset_student_attempts
    delete_module=delete_module
  File "/edx/app/edxapp/edx-platform/lms/djangoapps/instructor/enrollment.py", line 271, in reset_student_attempts
    _reset_module_attempts(module_to_reset)
  File "/edx/app/edxapp/edx-platform/lms/djangoapps/instructor/enrollment.py", line 281, in _reset_module_attempts
    problem_state = json.loads(studentmodule.state)
  File "/usr/lib/python2.7/json/__init__.py", line 338, in loads
    return _default_decoder.decode(s)
  File "/usr/lib/python2.7/json/decoder.py", line 366, in decode
    obj, end = self.raw_decode(s, idx=_w(s, 0).end())
TypeError: expected string or buffer
[24/Sep/2016 21:08:55] "POST /courses/course-v1:edX+DemoX+Demo_Course/instructor/api/reset_student_attempts HTTP/1.1" 500 84640

[xcompass]

@jleong-openedx could you take a look at it? Thanks.

[jleong-openedx]

Hi @natea, thank you for reporting this. Could you please let me know more about the state of the question when you attempted to delete the student state?

e.g. Had the final answer already been submitted? If the rationale text does not contain any sensitive information, would you be able to post it here so that I can try to reproduce the error?

Also, are you hosting this instance of Open edX yourself/do you have access to the server? If so, would you be able to let us know the version of Peer Instruction that you are working with? Thank you.

[xcompass]

maybe related to #119

[lenglund]

Will discuss further in #119.