Funny thing, this feature breaks the interactive interpreter in the most basic way on OS X systems.   For example, the tab key won't even work to indent.  You can't even type the most basic programs into the interactive interpreter. For example:

>>> for i in range(10):
...      print(i)

Oh sure, you can make it work by typing the space bar a bunch of times, but it's extremely annoying.  

The only way I was able to get a working interactive interpreter on my machine was to manually edit site.py and remove the call to enablerlcompleter() from main().

I hope someone reconsiders this feature and removes it as default behavior.