gnome 3.12 cannot be launched + locale does not he

Question

I have recently installed debian "testing" jessie RC betta. I wanted to personalized system-wide the gnome-terminal by changing the custom default terminal size in the file /usr/share/vte/termcap/xterm. In fact, I just changed with gedit the the col and li numbers in the following line :co#80:it#8:li#24:\. After I did that, I was not able to launch any more the gnome terminal 3.12.3. I got the following output:

~$ gnome-terminal
(process:2879): Gtk-WARNING **: Locale not supported by C library.
Using the fallback 'C' locale. 
Error constructing proxy for org.gnome.Terminal:/org/gnome/Terminal/Factory0: Error calling StartServiceByName for org.gnome.Terminal: GDBus.Error:org.freedesktop.DBus.Error.Spawn.ChildExited: Process org.gnome.Terminal exited with status 8

Of course I undo everything in the xterm file but it did not work out. I also reinstalled the gnome-terminal, but nothing.

I searched in the internet and found the same gnome-terminal's error here. Hence, I decided to check whether the "localte" setup could help me out. For that, I ran the following commands:

~$ localectl 
 System Locale: LANG=en_GB.UTF-8
                  LANGUAGE=en_GB:en
   VC Keymap: de
  X11 Layout: de
   X11 Model: pc105
 X11 Options: terminate:ctrl_alt_bksp
~$ sudo dpkg-reconfigure locales
~$ sudo locale-gen en_GB.UTF-8
~$ cat /etc/default/locale
#  File generated by update-locale
LANG=en_GB.UTF-8
LANGUAGE="en_GB:en"
~$ . /etc/default/locale

after it I just got rid of the Gtk-Warning. But the gnome-terminal still cannot be launched.

Do you think I need to regenerate the xterm file? if yes, how do I do that?

Thanks in advance.

PD: Btw, funny thing is that the "locale" setup goes away if I restart the computer. In order to keep it persistent, I had to export from my .bashrc the following environmental variables:

export LANGUAGE=en_GB.UTF-8
export LANG=en_GB.UTF-8
export LC_ALL=en_GB.UTF-8