It looks like the Exec[npm-install] failed. If you put the parameter 'logoutput => on_failure' into that exec (you should be able to find it in modules-0/grunt/manifests/init.pp:47) then you might have more of an idea as to why it failed.
Basically puppet tried to run a command on the VM and the command failed. Other stuff depended on that command working so the entire run fails.