% ./python -m test.regrtest test_asyncore
test_asyncore
Exception in thread Thread-3:
Traceback (most recent call last):
  File "/home/cpython/hg/2.7/Lib/threading.py", line 552, in __bootstrap_inner
    self.run()
  File "/home/cpython/hg/2.7/Lib/threading.py", line 505, in run
    self.__target(*self.__args, **self.__kwargs)
  File "/home/cpython/hg/2.7/Lib/test/test_asyncore.py", line 712, in <lambda>
    t = threading.Thread(target=lambda: asyncore.loop(timeout=0.1, count=500))
  File "/home/cpython/hg/2.7/Lib/asyncore.py", line 220, in loop
    poll_fun(timeout, map)
  File "/home/cpython/hg/2.7/Lib/asyncore.py", line 156, in poll
    read(obj)
  File "/home/cpython/hg/2.7/Lib/asyncore.py", line 87, in read
    obj.handle_error()
  File "/home/cpython/hg/2.7/Lib/asyncore.py", line 83, in read
    obj.handle_read_event()
  File "/home/cpython/hg/2.7/Lib/asyncore.py", line 443, in handle_read_event
    self.handle_accept()
  File "/home/cpython/hg/2.7/Lib/test/test_asyncore.py", line 487, in handle_accept
    sock, addr = self.accept()
TypeError: 'NoneType' object is not iterable

Exception in thread Thread-4:
Traceback (most recent call last):
  File "/home/cpython/hg/2.7/Lib/threading.py", line 552, in __bootstrap_inner
    self.run()
  File "/home/cpython/hg/2.7/Lib/threading.py", line 505, in run
    self.__target(*self.__args, **self.__kwargs)
  File "/home/cpython/hg/2.7/Lib/test/test_asyncore.py", line 712, in <lambda>
    t = threading.Thread(target=lambda: asyncore.loop(timeout=0.1, count=500))
  File "/home/cpython/hg/2.7/Lib/asyncore.py", line 220, in loop
    poll_fun(timeout, map)
  File "/home/cpython/hg/2.7/Lib/asyncore.py", line 156, in poll
    read(obj)
  File "/home/cpython/hg/2.7/Lib/asyncore.py", line 87, in read
    obj.handle_error()
  File "/home/cpython/hg/2.7/Lib/asyncore.py", line 83, in read
    obj.handle_read_event()
  File "/home/cpython/hg/2.7/Lib/asyncore.py", line 443, in handle_read_event
    self.handle_accept()
  File "/home/cpython/hg/2.7/Lib/test/test_asyncore.py", line 487, in handle_accept
    sock, addr = self.accept()
TypeError: 'NoneType' object is not iterable

1 test OK.
[43391 refs]

Sample buildbot run that failed: http://buildbot.python.org/all/builders/SPARC64%20Solaris%2010%20%5BSB%5D%202.7/builds/69/steps/test/logs/stdio

Haven't investigated yet.