From #19535:
$ ./python -OO -m test -v test_email 

[...]

======================================================================
ERROR: test_policy (unittest.loader.ModuleImportFailure)
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Traceback (most recent call last):
  File "/home/wolf/dev/py/py3k/Lib/unittest/case.py", line 57, in testPartExecutor
    yield
  File "/home/wolf/dev/py/py3k/Lib/unittest/case.py", line 571, in run
    testMethod()
  File "/home/wolf/dev/py/py3k/Lib/unittest/loader.py", line 32, in testFailure
    raise exception
ImportError: Failed to import test module: test_policy
Traceback (most recent call last):
  File "/home/wolf/dev/py/py3k/Lib/unittest/loader.py", line 272, in _find_tests
    module = self._get_module_from_name(name)
  File "/home/wolf/dev/py/py3k/Lib/unittest/loader.py", line 250, in _get_module_from_name
    __import__(name)
  File "/home/wolf/dev/py/py3k/Lib/test/test_email/test_policy.py", line 5, in <module>
    import email.policy
  File "/home/wolf/dev/py/py3k/Lib/email/policy.py", line 22, in <module>
    class EmailPolicy(Policy):
  File "/home/wolf/dev/py/py3k/Lib/email/_policybase.py", line 101, in _extend_docstrings
    cls.__doc__ = _append_doc(cls.__bases__[0].__doc__, cls.__doc__)
  File "/home/wolf/dev/py/py3k/Lib/email/_policybase.py", line 95, in _append_doc
    doc = doc.rsplit('\n', 1)[0]
AttributeError: 'NoneType' object has no attribute 'rsplit'

----------------------------------------------------------------------
Ran 68 tests in 0.028s

FAILED (errors=11)
Warning -- sys.path was modified by test_email
test test_email failed
1 test failed:
    test_email