edx/edx-ora — pull request #123 by dcadams (2013-08-07 20:05:45+00:00)
Title: Fix for dupes in the calibrationhistory table

A new function to check for dupes in calibrationhistory table
and if found it deletes all but that with the lowest id for
that student_id, location.
Includes an updated unit test that exercises the new function.