I'm on Ubuntu 5.10, with Python 2.4.2-0ubuntu2, and
when I open a terminal window and run python, I get

>>> import locale
>>> locale.getpreferredencoding()
Traceback (most recent call last):
  File "<stdin>", line 1, in ?
  File "/usr/lib/python2.4/locale.py", line 417, in
getpreferredencoding
    setlocale(LC_CTYPE, "")
  File "/usr/lib/python2.4/locale.py", line 381, in
setlocale
    return _setlocale(category, locale)
locale.Error: unsupported locale setting

However, if I su - root - or even su right back to my
own account (catherine) ! - then everything works.

This is of concern (to me, anyway) because this error
crashes bzr. 

I chose "Esperanto" as my language when setting up
Ubuntu.  (No, I wasn't trying to be funny - I really do
speak Esperanto!)  That may be why I found the problem,
but I don't think this is simply a problem with flawed
Esperanto support in Ubuntu - because the routine works
after su is used, and because
locale.nl_langinfo(CODESET) works fine (please read on).

Anyway, within locale.getpreferredencoding(), line 417
- setlocale(LC_CTYPE, "") - seems to be the problem...

>>> locale.setlocale(locale.LC_CTYPE)
'C'
>>> locale.setlocale(locale.LC_CTYPE, "")
Traceback (most recent call last):
  File "<stdin>", line 1, in ?
  File "/usr/lib/python2.4/locale.py", line 381, in
setlocale
    return _setlocale(category, locale)
locale.Error: unsupported locale setting
>>> locale.setlocale(locale.LC_CTYPE, None)
'C'

This makes me wonder if setlocale(LC_TYPE, "") is
really so very necessary.  It seems to be there to prep
for the nl_langinfo call, but it doesn't actually seem
strictly necessary for that call to work.

>>> locale.nl_langinfo(locale.CODESET)
'ANSI_X3.4-1968'

... I get that result whether before or after calling
setlocale, and I get it under any account (including
root, where setlocale does not raise an exception).

Thus, as far as I can tell, it isn't really necessary
to set setlocale(LC_CTYPE, "") or die trying, and
accepting the nl_langinfo result without a 
successful setlocale(LC_CTYPE, "") would be preferable
to raising an unhandled exception.  I suggest that
setlocale(LC_TYPE, "") be enclosed in a try block.

                try:
                    setlocale(LC_CTYPE, "")
                except:
                    None

Since I don't really understand what it's doing in the
first place, I don't know if this is really a good patch.

Thanks!