'defaults' command doesn't read plists anymore; use PlistBuddy instead

[snej]

The script uses the defaults command to read the bundle version from the app's Info.plist. Unfortunately defaults doesn't support that anymore — as threatened in its man page, it's stopped working on anything but actual registered defaults domains. (I don't know when this changed, but this is how it is in El Capitan.)

Instead, use PlistBuddy; for example to get the bundle version:

/usr/libexec/PlistBuddy MyApp.app/Contents/Info.plist -c 'Print CFBundleVersion'