Martin von Zweigbergk <martinvonz@google.com> [Mon, 20 Jul 2015 13:39:25 -0700] rev 25896
exchange: fix dead assignment
The assignment of the value from bundle2.processbundle() to 'r' is
unused. It is currently the same as its third argument (if given), and
since that argument may eventually go away (according to the method's
docstring), let's reassign the return value to 'op' instead to better
prepare for that.