On 2.7, I get the following crashes in test_pydoc:

======================================================================
FAIL: test_apropos_with_bad_package (test.test_pydoc.PydocImportTest)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/home/antoine/cpython/27/Lib/test/test_pydoc.py", line 316, in test_apropos_with_bad_package
    result = run_pydoc('nothing', '-k', PYTHONPATH=TESTFN)
  File "/home/antoine/cpython/27/Lib/test/test_pydoc.py", line 185, in run_pydoc
    rc, out, err = assert_python_ok('-B', pydoc.__file__, *args, **env)
  File "/home/antoine/cpython/27/Lib/test/script_helper.py", line 49, in assert_python_ok
    return _assert_python(True, *args, **env_vars)
  File "/home/antoine/cpython/27/Lib/test/script_helper.py", line 41, in _assert_python
    "stderr follows:\n%s" % (rc, err.decode('ascii', 'ignore')))
AssertionError: Process return code is -6, stderr follows:
python: Objects/object.c:65: _Py_AddToAllObjects: Assertion `(op->_ob_prev == ((void *)0)) == (op->_ob_next == ((void *)0))' failed.

======================================================================
FAIL: test_apropos_with_unreadable_dir (test.test_pydoc.PydocImportTest)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/home/antoine/cpython/27/Lib/test/test_pydoc.py", line 326, in test_apropos_with_unreadable_dir
    result = run_pydoc('nothing', '-k', PYTHONPATH=TESTFN)
  File "/home/antoine/cpython/27/Lib/test/test_pydoc.py", line 185, in run_pydoc
    rc, out, err = assert_python_ok('-B', pydoc.__file__, *args, **env)
  File "/home/antoine/cpython/27/Lib/test/script_helper.py", line 49, in assert_python_ok
    return _assert_python(True, *args, **env_vars)
  File "/home/antoine/cpython/27/Lib/test/script_helper.py", line 41, in _assert_python
    "stderr follows:\n%s" % (rc, err.decode('ascii', 'ignore')))
AssertionError: Process return code is -6, stderr follows:
python: Objects/object.c:65: _Py_AddToAllObjects: Assertion `(op->_ob_prev == ((void *)0)) == (op->_ob_next == ((void *)0))' failed.


"hg bisect" tells me the first offending revision is 45862f4ab1c5, but that doesn't tell much, since it's just the revision which introduced the tests.

Hmm, it seems it's due to a 3rd party C extension:

$ ./python -c "import sqlalchemy.cprocessors"
python: Objects/object.c:65: _Py_AddToAllObjects: Assertion `(op->_ob_prev == ((void *)0)) == (op->_ob_next == ((void *)0))' failed.

Closing as not a Python bug.