Sorry for the delay. I've run the tests (with OpenSSL 1.0.1-beta3) in debug mode and got an error:

======================================================================
ERROR: test_npn_ext (test.test_ssl.ThreadedTests)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/home/antoine/cpython/default/Lib/test/test_ssl.py", line 1882, in test_npn_ext
    chatty=True, connectionchatty=True)
  File "/home/antoine/cpython/default/Lib/test/test_ssl.py", line 1210, in server_params_test
    s.connect((HOST, server.port))
  File "/home/antoine/cpython/default/Lib/ssl.py", line 543, in connect
    self._real_connect(addr, False)
  File "/home/antoine/cpython/default/Lib/ssl.py", line 533, in _real_connect
    self.do_handshake()
  File "/home/antoine/cpython/default/Lib/ssl.py", line 513, in do_handshake
    self._sslobj.do_handshake()
ssl.SSLError: [Errno 1] _ssl.c:434: error:140920E3:SSL routines:SSL3_GET_SERVER_HELLO:parse tlsext


I've determined that this is because of the use of strlen() on a non-zero terminated string. I'll try to come up with an updated patch.