Running tests with a non-US locale

For some reason, gettext() on my Linux machine has decided that it would
like to translate some of Subversion's output to UK English.
Specifically, 'Authorization failed' now has the UK variant spelling
'Authorisation failed'.

Much as I appreciate this behaviour, it's breaking at least the authz
tests. Contrary to what sussman just suggested in IRC, there _are_
other locales besides US, so I assume other people already encounter this
- what do you do to solve it? And more interestingly, is there some way
we can fix this in the test scripts themselves?

The only fix I've found is to run the tests with e.g.
LANGUAGE=en_US.UTF-8 - is that suitable to include into the test
framework somewhere? Alternatively, 'LANGUAGE= LANG=en_US.UTF-8 ...'
works as well, of course. Either way, don't know whether we can rely on
UTF-8 support...

Regards,
Malcolm