Incorrect locale if the host's locale is not present in the desktop next ISO

If unity8-lxc-setup is run from a host with a locale that is not included in the desktop next iso (which has only got a few language packs installed), there are a few warnings shown during the setup:

http://pastebin.ubuntu.com/11724558/

The issue is that the host's locale is not recognized and in the container it is then set as "POSIX" upon failure to recognize it. "POSIX" is an invalid locale name, which then prevents Mir from starting in the unity8 session.

The workaround for this after the setup is to generate the locale inside the container. In this particular case, it was the 'ca' locale:

root@unity8-lxc:~# locale-gen ca
Generating locales...
  ca_AD.UTF-8... done
  ca_ES.UTF-8... done
  ca_ES.UTF-8@valencia... done
  ca_FR.UTF-8... done
  ca_IT.UTF-8... done
Generation complete.
root@unity8-lxc:~# locale
LANG=ca_ES.UTF-8
LANGUAGE=ca_ES
LC_CTYPE="ca_ES.UTF-8"
LC_NUMERIC=ca_ES.UTF-8
LC_TIME=ca_ES.UTF-8
LC_COLLATE="ca_ES.UTF-8"
LC_MONETARY=ca_ES.UTF-8
LC_MESSAGES="ca_ES.UTF-8"
LC_PAPER=ca_ES.UTF-8
LC_NAME=ca_ES.UTF-8
LC_ADDRESS=ca_ES.UTF-8
LC_TELEPHONE=ca_ES.UTF-8
LC_MEASUREMENT=ca_ES.UTF-8
LC_IDENTIFICATION=ca_ES.UTF-8
LC_ALL=

Here's an explanation of why this might be happening: http://askubuntu.com/a/144448/9781

Perhaps the best thing to do would be for unity8-lxc-setup to run locale-gen if it detects that the host locale is not recognized? Or to simply add a step to run locale-gen regardless, which might be much simpler and less error-prone.