travis build, bug fixes

Why did you change `N_()`  to `_()`? 

`N_()` is correct for constants here, see https://github.com/webyast/webyast/wiki/Localization#translating-constants

(Note: `N_()` works even after the language is changed, using `_()` in constants mean that the string is translated once at start using the initial locale, it cannot be retranslated later.)