fix an exception not correctly reporting if the locale is not set

I was having issues on my OSX 10.8, python 2.7.5 system where exceptions were not correctly reporting.

```
Traceback (most recent call last):
  File "/usr/local/bin/pelican", line 9, in <module>
    load_entry_point('pelican==3.3', 'console_scripts', 'pelican')()
  File "/Users/russ/Projects/repositories/pelican/pelican/__init__.py", line 393, in main
    msg = msg.decode(locale.getpreferredencoding(False))
LookupError: unknown encoding: 
```

The boolean argument is `do_setlocale` according to the python documentation says this:

> On some systems, it is necessary to invoke setlocale() to obtain the user preferences, so this function is not thread-safe. If invoking setlocale is not necessary or desired, do_setlocale should be set to False.

I'm not all that familiar with the codebase, but I have been running the system with the boolean removed and it seems to be behaving well.