Comment 78 for bug 1246272

And one more link I googled out, somewhat related as it shows thise priority problems: .dmrc is read by display manager, but can also be generated by it, and if it exists it can be read, but need not if AccountsService is available, … Brrrrrr
https://afrantzis.wordpress.com/2012/06/11/changing-gdmlightdm-user-login-settings-programmatically/