The command grunt imagemin
output the following to a random file.
Fatal error: ENOENT, no such file or directory \'app/public/assets/img/epg/rec
Uninstalling version 0.5.0 and going back to version 0.3.0 with the following commands should restore the prior functionality:
npm uninstall grunt-contrib-imagemin
npm install --save-dev grunt-contrib-imagemin@0.3.0
There is an issue, https://github.com/gruntjs/grunt-contrib-imagemin/issues/140, that is being worked on, and when it is fixed it should be safe to upgrade.