[luatex] annoying locale error

[Werner LEMBERG]

>> it seems that luatex is sensitive to very subtle details
>> that can easily be missed (for example, `-` vs. `_`).
> 
> To be fair, Werner, every programming language with which I am
> familiar treats '-' vs. '_' as totally different characters — LuaTeX
> is hardly anomalous here ...

Oh, I'm not talking about programming languages!  It's rather that in
locales you have to use `_` *and* `-`, and it's easy to mix them up.

For example, a call to `locale` on my GNU/Linux box gives

```
LANG=en_US.UTF-8
LC_CTYPE="en_US.UTF-8"
LC_NUMERIC="en_US.UTF-8"
LC_TIME="en_US.UTF-8"
LC_COLLATE="en_US.UTF-8"
LC_MONETARY="en_US.UTF-8"
LC_MESSAGES="en_US.UTF-8"
LC_PAPER="en_US.UTF-8"
LC_NAME="en_US.UTF_8"
LC_ADDRESS="en_US.UTF-8"
LC_TELEPHONE="en_US.UTF-8"
LC_MEASUREMENT="en_US.UTF-8"
LC_IDENTIFICATION="en_US.UTF-8"
LC_ALL=
```

I've introduced a typo in the above listing – did you notice it?


    Werner