Test 75 test_contextlib fails. 
Fatal Python error: Objects/frameobject.c:429 object at 0x10fa32178 has negative ref count -2604246222170760230
Exception: Child error on test_contextlib: Exit code -6

Thread hangs and must be force exited on Mac OSX 10.10.3
Problem with threading.

Stack trace:
[ 75/393] test_contextlib
Fatal Python error: Objects/frameobject.c:429 object at 0x10fa32178 has negative ref count -2604246222170760230

Current thread 0x00007fff73b07300 (most recent call first):
  File "/Users/rainierharvey/Documents/cs/openSource/cpython/Lib/unittest/case.py", line 579 in run
  File "/Users/rainierharvey/Documents/cs/openSource/cpython/Lib/unittest/case.py", line 627 in __call__
  File "/Users/rainierharvey/Documents/cs/openSource/cpython/Lib/unittest/suite.py", line 122 in run
  File "/Users/rainierharvey/Documents/cs/openSource/cpython/Lib/unittest/suite.py", line 84 in __call__
  File "/Users/rainierharvey/Documents/cs/openSource/cpython/Lib/unittest/suite.py", line 122 in run
  File "/Users/rainierharvey/Documents/cs/openSource/cpython/Lib/unittest/suite.py", line 84 in __call__
  File "/Users/rainierharvey/Documents/cs/openSource/cpython/Lib/unittest/suite.py", line 122 in run
  File "/Users/rainierharvey/Documents/cs/openSource/cpython/Lib/unittest/suite.py", line 84 in __call__
  File "/Users/rainierharvey/Documents/cs/openSource/cpython/Lib/test/support/__init__.py", line 1674 in run
  File "/Users/rainierharvey/Documents/cs/openSource/cpython/Lib/test/support/__init__.py", line 1775 in _run_suite
  File "/Users/rainierharvey/Documents/cs/openSource/cpython/Lib/test/support/__init__.py", line 1809 in run_unittest
  File "/Users/rainierharvey/Documents/cs/openSource/cpython/Lib/test/regrtest.py", line 1279 in test_runner
  File "/Users/rainierharvey/Documents/cs/openSource/cpython/Lib/test/regrtest.py", line 1280 in runtest_inner
  File "/Users/rainierharvey/Documents/cs/openSource/cpython/Lib/test/regrtest.py", line 978 in runtest
  File "/Users/rainierharvey/Documents/cs/openSource/cpython/Lib/test/regrtest.py", line 532 in main
  File "/Users/rainierharvey/Documents/cs/openSource/cpython/Lib/test/regrtest.py", line 1564 in main_in_temp_cwd
  File "/Users/rainierharvey/Documents/cs/openSource/cpython/Lib/test/regrtest.py", line 1589 in <module>
  File "/Users/rainierharvey/Documents/cs/openSource/cpython/Lib/runpy.py", line 85 in _run_code
  File "/Users/rainierharvey/Documents/cs/openSource/cpython/Lib/runpy.py", line 170 in _run_module_as_main
Traceback (most recent call last):
  File "/Users/rainierharvey/Documents/cs/openSource/cpython/Lib/runpy.py", line 170, in _run_module_as_main
    "__main__", mod_spec)
  File "/Users/rainierharvey/Documents/cs/openSource/cpython/Lib/runpy.py", line 85, in _run_code
    exec(code, run_globals)
  File "/Users/rainierharvey/Documents/cs/openSource/cpython/Lib/test/__main__.py", line 3, in <module>
    regrtest.main_in_temp_cwd()
  File "/Users/rainierharvey/Documents/cs/openSource/cpython/Lib/test/regrtest.py", line 1564, in main_in_temp_cwd
    main()
  File "/Users/rainierharvey/Documents/cs/openSource/cpython/Lib/test/regrtest.py", line 738, in main
    raise Exception("Child error on {}: {}".format(test, result[1]))
Exception: Child error on test_contextlib: Exit code -6
^CException ignored in: <module 'threading' from '/Users/rainierharvey/Documents/cs/openSource/cpython/Lib/threading.py'>
Traceback (most recent call last):
  File "/Users/rainierharvey/Documents/cs/openSource/cpython/Lib/threading.py", line 1297, in _shutdown
    t.join()
  File "/Users/rainierharvey/Documents/cs/openSource/cpython/Lib/threading.py", line 1063, in join
    self._wait_for_tstate_lock()
  File "/Users/rainierharvey/Documents/cs/openSource/cpython/Lib/threading.py", line 1079, in _wait_for_tstate_lock
    elif lock.acquire(block, timeout):

Thanks for the report.  This problem has just been fixed.  Please update and try again.

(See Issue22906 for details.)