Misleading error message shown if translation fails

[feri]

'midgardmvc build_translations' will show the above message if translation fails:

   ! Can't find msgfmt tool. Skipping generation of gettext-translations

This is slightly misleading, since 'msgfmt' is available. It returned an error code, other than 0. There are several reasons of an error, a very common one is to have duplicated strings.

Would be better if the output of msgfmt is preserved and shown to the user.