Which causes the locale machinery to spit exceptions, and the program to 
die, usually (eg, hg).

This manifests naturally on an Intel Mac, Mac OS X 10.5.7, but the 
problem behavior is in _build_localename.  When called as

_build_localename((None,'any_string'))

it returns 'C.any_string'.  I don't know of any system that supports 
anything but the POSIX portable character set in the C/POSIX locale, so
this is clearly wrong.

I suggest that when the first component of the argument is None, the
second component should be ignored.

Probably my Mac is misconfigured, but I think this is still a bug that 
should be fixed.

Observed in all of 2.5.4, 2.6.2, and 3.0.1 (vanilla MacPorts builds).

References: It's possible this is related to issue1699853, issue1176504, 
issue504219, but I don't think fixing this will help with those issues.  
It is not related to issue3067.