Comment 7 for bug 859814

Some more data here, the following results in postgresql not started on installation:

$ LC_ALL=en_GB.UTF-8 ssh ubuntu@$HOSTNAME
$ sudo apt-get install postgresql-9.1
...
Adding user postgres to group ssl-cert
Building PostgreSQL dictionaries from installed myspell/hunspell packages...
Setting up postgresql-9.1 (9.1.3-2) ...
Error: The locale requested by the environment is invalid.
Error: could not create default cluster. Please create it manually with

  pg_createcluster 9.1 main --start

or a similar command (see 'man pg_createcluster').

If you run 'apt-get install language-pack-en' prior to running the above, it will work.

It will still fail, though if you do:
 $ LC_ALL=fr_FR.UTF-8 ssh ....
 $ sudo apt-get install postgresql-9.1
(which would be fixed by 'apt-get install language-pack-fr').