If you have Lytro Desktop installed on that computer, and you've used the camera with it, Lytro Desktop will automatically pull the calibration data to a default location. If this is the case, Power Tools should automatically use this default location for calibration and you shouldn't need to specify
--calibration-in as an argument.
If you're running an issue, please copy/paste output from the error and post to the Power Tools forums.
You can manually verify that the calibration data is in the default location:
- OS X: