Random exception when running unit tests.

[ErikW]

After upgrading to Django 1.7, my test suite now randomly throws this exception 80% of the time. Not sure why this would happen intermittently like this.

======================================================================
ERROR: test_get_list_json (api.tests.test_user_drf.UserResourceTest)
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Traceback (most recent call last):
  File "/Users/erik/Dropbox/home/git/proj/api/tests/test_user_drf.py", line 48, in test_get_list_json
    resp = self.client.get('/api/drf/user/', content_type="application/json", HTTP_AUTHORIZATION=self.get_credentials())
  File "/Users/erik/.virtualenvs/proj/src/django-tastypie/tastypie/test.py", line 68, in get
    return self.client.get(uri, **kwargs)
  File "/Users/erik/.virtualenvs/proj/lib/python2.7/site-packages/django/test/client.py", line 467, in get
    **extra)
  File "/Users/erik/.virtualenvs/proj/lib/python2.7/site-packages/django/test/client.py", line 285, in get
    return self.generic('GET', path, secure=secure, **r)
  File "/Users/erik/.virtualenvs/proj/lib/python2.7/site-packages/django/test/client.py", line 355, in generic
    return self.request(**r)
  File "/Users/erik/.virtualenvs/proj/lib/python2.7/site-packages/django/test/client.py", line 419, in request
    response = self.handler(environ)
  File "/Users/erik/.virtualenvs/proj/lib/python2.7/site-packages/django/test/client.py", line 110, in __call__
    response = self.get_response(request)
  File "/Users/erik/.virtualenvs/proj/lib/python2.7/site-packages/django/core/handlers/base.py", line 210, in get_response
    response._closable_objects.append(request)
AttributeError: 'Response' object has no attribute '_closable_objects'

----------------------------------------------------------------------
Ran 1 test in 0.322s

FAILED (errors=1)
Destroying test database for alias 'default'...

[Keryn Knight]

Response is, AFAIK, a DRF thing, and there's an open ticket on the DRF issue tracker ​here which seems a likely candidate. Possibly the problem exists in either DRF or tastypie? (Both are listed in your stacktrace)

[ErikW]

This is definitely related to caching. When I flush my cache, the tests run fine, but if I immediately run it a seconds time before the cached objects have expired, I get the traceback.

It looks like _closed_objects isn't serialized when the objects are pickled for caching.

This doesn't seem to be limited to a particular backend -- I've tested with FileBasedCache, Memcached,and Redis.

[ErikW]

kezabelle: didn't see your response before I posted about caching. I'll take a look at those other issues...

[Claude Paroz]

The root cause if this issue is DRF excluding _closable_objects from cached (pickled) response objects. Tom or Xavier could explain why pickling _closable_objects may be problematic, and then open a separate ticket about that problem.