r73001 for Issue5150 added the Rstrip extension to IDLE and modified the extensions configuration file, config-extensions.def, to enable it by default.  For Python 2 OS X installs, however, the config-extensions.def file from Lib/idlelib is replaced by a tailored one from Mac/IDLE and the changes for Issue5101 are lost.  The attached patch updates the Mac/IDLE version appropriately.  Note, for Python 3 installs, this is not a problem as there is no longer a separate Mac-only copy of the file.