Try this:
- Rename the folder /Users/msalomon/Library/Arduino15 to /Users/msalomon/Library/Arduino15.bak.
- Restart the Arduino IDE.
Note that the above will cause any boards you have installed via Boards Manager to disappear. You can reinstall them but first do a test to verify the problem is resolved. If there is no problem you are free to delete /Users/msalomon/Library/Arduino15.bak. You can copy over preferences.txt from that folder with the Arduino IDE shut down if you want your old preferences back or you can just reconfigure them. The problem is somehow related to Boards Manager package installations going wrong, maybe an Arduino AVR Boards update or another 3rd party package interfering with Arduino AVR Boards. There were some issues with this around Arduino IDE 1.6.9 (though I remember it being 1.6.10 instead) so you might consider updating to the latest version of the Arduino IDE unless there is a specific reason for you to use Arduino IDE 1.6.9.