When updating the boards file you need to update the jason with three piece of information from the https://github.com/ljunquera/arduino-smartwatch-boards release by running:
Example for File Size:
stat -f %z arduino-smartwatch-boards-0.1.1.tar.gz
Example for MD5:
md5 arduino-smartwatch-boards-0.1.1.tar.gz