Comment 3 for bug 1164083

I confirm this on a up-to-date ubuntu 14.04 amd64 server installation. My X server is running on a different machine.

Running gnome-terminal gives:
Fontconfig warning: ignoring C.UTF-8: not a valid language tag

Maybe I could change locale settings to workaround this, but it is bug and there seems to be a fix available.

$ locale
LANG=C.UTF-8
LANGUAGE=
LC_CTYPE="C.UTF-8"
LC_NUMERIC=pt_PT.UTF-8
LC_TIME=pt_PT.UTF-8
LC_COLLATE="C.UTF-8"
LC_MONETARY=pt_PT.UTF-8
LC_MESSAGES="C.UTF-8"
LC_PAPER=pt_PT.UTF-8
LC_NAME=pt_PT.UTF-8
LC_ADDRESS=pt_PT.UTF-8
LC_TELEPHONE=pt_PT.UTF-8
LC_MEASUREMENT=pt_PT.UTF-8
LC_IDENTIFICATION=pt_PT.UTF-8
LC_ALL=