When Python is compiled with readline, repeatedly pressing <TAB> key in repl breaks the repl prompt.

Below is what I see when I hit <TAB> 4 times.

    yury@ysmac ~/dev/py/cpython $ ./python.exe
    Python 3.5.0+ (3.5:4ae62ddf7bc7+, Nov 18 2015, 14:52:57)
    [GCC 4.2.1 Compatible Apple LLVM 7.0.0 (clang-700.1.76)] on darwin
    Type "help", "copyright", "credits" or "license" for more information.
    >>>

    >>>

    >>>

    >>>


Reproducible when Python is built from source on latest OS X.  Works OK when installed from MacPorts.

Further, if I add

   PyOS_ReadlineFunctionPointer = PyOS_StdioReadline;

in PyOS_Readline in myreadline.c, everything works as expected, so I think this is a readline bug.