If you are upgrading from a version earlier than 1.17
The theme now includes a vivacity.pot translation file instead of vivacity.po and vivacity.mo files. This file is identical to vivacity.po and when saved generates the .po and .mo files. Nothing has changed, you still need vivacity.po and vivacity.mo and they can stay in the vivacity/languages/ folder but you now also have the option of adding these files to wp-content/languages/themes/ or inside your child theme so they are not overwritten when updating the theme. For more information please see Translating The Theme (Localisation).