Added invalid.user error message and made second arg to error_message_and_field optional.
Added invalid.user error message and made second arg to error_message_and_field optional.

mccarrmb/moztrap,bobsilverberg/moztrap,bobsilverberg/moztrap,shinglyu/moztrap,mccarrmb/moztrap,mccarrmb/moztrap,shinglyu/moztrap,mozilla/moztrap,mozilla/moztrap,mozilla/moztrap,shinglyu/moztrap,mccarrmb/moztrap,bobsilverberg/moztrap,shinglyu/moztrap,mccarrmb/moztrap,bobsilverberg/moztrap,mozilla/moztrap,shinglyu/moztrap,mozilla/moztrap