TestCase.assertWarns doesn't work when using django's test runner.

[Matt3o12]

Django's test runner (python manage.py test) doesn't seem to be supporting TestCase.assertWarns using a freshly created project.
There is a testcase where django fails:

from unittest.case import TestCase
import warnings

class TestWarning(TestCase):
    def testAssertWarns(self):
        # should just pass

        with self.assertWarns(UserWarning):
            warnings.warn("Hello world.", UserWarning)

    def testAssertWarnsRegex(self):
        with self.assertWarnsRegex(UserWarning, "Hello world\."):
            warnings.warn("Hello world.")

When I run $ python manage.py test, I always end up getting:

======================================================================
ERROR: testAssertWarns (myapp.tests.TestWarning)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/private/tmp/djago/myproj/myapp/tests.py", line 9, in testAssertWarns
    with self.assertWarns(UserWarning):
  File "/usr/local/Cellar/python3/3.4.2_1/Frameworks/Python.framework/Versions/3.4/lib/python3.4/unittest/case.py", line 205, in __enter__
    for v in sys.modules.values():
RuntimeError: dictionary changed size during iteration

======================================================================
ERROR: testAssertWarnsRegex (myapp.tests.TestWarning)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/private/tmp/djago/myproj/myapp/tests.py", line 13, in testAssertWarnsRegex
    with self.assertWarnsRegex(UserWarning, "Hello world\."):
  File "/usr/local/Cellar/python3/3.4.2_1/Frameworks/Python.framework/Versions/3.4/lib/python3.4/unittest/case.py", line 205, in __enter__
    for v in sys.modules.values():
RuntimeError: dictionary changed size during iteration

----------------------------------------------------------------------

When I just run $ python -m unittest, these two tests pass. I've tested that on django 1.6 (using python 3.3) and django 1.7 (using python 3.3 and 3.4) and

[Thomas C]

This seems to be related ​https://bitbucket.org/gutworth/six/issue/68/assertwarns-and-six. six has been upgraded to 1.8.0 on master and I can't reproduce it (although I can with an older checkout).

[Thomas C]

I'm closing this ticket as six upgrade to 1.8.0 has been backported to Django 1.6.9 (see ​https://github.com/django/django/commit/81477c91f68d7091f8da417a030dd4b9b776b70a). Upgrading Django to that version (once it is released) will most likely resolve your problem.