The changes are also causing segfaults when readline is linked with BSD libedit (the default on OS X) rather than GNU readline:

======================================================================
FAIL: test_init (test.test_readline.TestReadline)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/py/dev/3x/source/Lib/test/test_readline.py", line 52, in test_init
    TERM='xterm-256color')
  File "/py/dev/3x/source/Lib/test/script_helper.py", line 69, in assert_python_ok
    return _assert_python(True, *args, **env_vars)
  File "/py/dev/3x/source/Lib/test/script_helper.py", line 55, in _assert_python
    "stderr follows:\n%s" % (rc, err.decode('ascii', 'ignore')))
AssertionError: Process return code is -11, stderr follows:
Fatal Python error: Segmentation fault

Current thread 0x00007fff75489310 (most recent call first):
  File "<frozen importlib._bootstrap>", line 321 in _call_with_frames_removed
  File "<frozen importlib._bootstrap>", line 1664 in load_module
  File "<frozen importlib._bootstrap>", line 540 in _check_name_wrapper
  File "<frozen importlib._bootstrap>", line 1110 in _load_backward_compatible
  File "<frozen importlib._bootstrap>", line 1140 in _load_unlocked
  File "<frozen importlib._bootstrap>", line 2175 in _find_and_load_unlocked
  File "<frozen importlib._bootstrap>", line 2186 in _find_and_load
  File "<string>", line 1 in <module>