There are various locale related bugs in various versions of boost,
where exceptions are thrown in boost::filesystem APIs when the
current locale is not to boost's liking. It's not clear what "not
to boost's liking" means in detail, though "en" and "en_US.UTF-8"
are not to its liking.
Fix it by running a test function that's known to throw in such
a case, and resetting LANG and LC_ALL to C if an exception is
thrown. In simplewallet, the locale is queried before that so the
correct translations will still be used.
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