Crap. I expected the set_reentrant() bug to be fixed, but I saw it one more time on the latest build (revision 0da4532a893389bd1ee1ddfe8227750d968023ba):

http://buildbot.python.org/all/builders/s390x%20RHEL%203.x/builds/817/steps/test/logs/stdio

0:02:54 [103/400] test_tracemalloc
python: ./Modules/_tracemalloc.c:194: set_reentrant: Assertion `PyThread_get_key_value(tracemalloc_reentrant_key) == ((PyObject *) &_Py_TrueStruct)' failed.
Fatal Python error: Aborted

Current thread 0x000003fffcd7b6f0 (most recent call first):
  File "/home/dje/cpython-buildarea/3.x.edelsohn-rhel-z/build/Lib/test/test_tracemalloc.py", line 94 in setUp
  File "/home/dje/cpython-buildarea/3.x.edelsohn-rhel-z/build/Lib/unittest/case.py", line 596 in run
  File "/home/dje/cpython-buildarea/3.x.edelsohn-rhel-z/build/Lib/unittest/case.py", line 648 in __call__
  File "/home/dje/cpython-buildarea/3.x.edelsohn-rhel-z/build/Lib/unittest/suite.py", line 122 in run
  File "/home/dje/cpython-buildarea/3.x.edelsohn-rhel-z/build/Lib/unittest/suite.py", line 84 in __call__
  File "/home/dje/cpython-buildarea/3.x.edelsohn-rhel-z/build/Lib/unittest/suite.py", line 122 in run
  File "/home/dje/cpython-buildarea/3.x.edelsohn-rhel-z/build/Lib/unittest/suite.py", line 84 in __call__
  File "/home/dje/cpython-buildarea/3.x.edelsohn-rhel-z/build/Lib/unittest/runner.py", line 176 in run
  File "/home/dje/cpython-buildarea/3.x.edelsohn-rhel-z/build/Lib/test/support/__init__.py", line 1802 in _run_suite
  File "/home/dje/cpython-buildarea/3.x.edelsohn-rhel-z/build/Lib/test/support/__init__.py", line 1836 in run_unittest
  File "/home/dje/cpython-buildarea/3.x.edelsohn-rhel-z/build/Lib/test/test_tracemalloc.py", line 989 in test_main
  File "/home/dje/cpython-buildarea/3.x.edelsohn-rhel-z/build/Lib/test/libregrtest/runtest.py", line 162 in runtest_inner
  File "/home/dje/cpython-buildarea/3.x.edelsohn-rhel-z/build/Lib/test/libregrtest/runtest.py", line 115 in runtest
  File "/home/dje/cpython-buildarea/3.x.edelsohn-rhel-z/build/Lib/test/libregrtest/main.py", line 306 in run_tests_sequential
  File "/home/dje/cpython-buildarea/3.x.edelsohn-rhel-z/build/Lib/test/libregrtest/main.py", line 367 in run_tests
  File "/home/dje/cpython-buildarea/3.x.edelsohn-rhel-z/build/Lib/test/libregrtest/main.py", line 405 in main
  File "/home/dje/cpython-buildarea/3.x.edelsohn-rhel-z/build/Lib/test/libregrtest/main.py", line 446 in main
  File "/home/dje/cpython-buildarea/3.x.edelsohn-rhel-z/build/Lib/test/libregrtest/main.py", line 468 in main_in_temp_cwd
  File "/home/dje/cpython-buildarea/3.x.edelsohn-rhel-z/build/Lib/test/__main__.py", line 3 in <module>
  File "/home/dje/cpython-buildarea/3.x.edelsohn-rhel-z/build/Lib/runpy.py", line 85 in _run_code
  File "/home/dje/cpython-buildarea/3.x.edelsohn-rhel-z/build/Lib/runpy.py", line 184 in _run_module_as_main
make: *** [buildbottest] Aborted