!!! All ebuilds that could satisfy "app-shells/bash-completion" have been masked. !!! One of the following masked packages is required to complete your request: - app-shells/bash-completion-1.2 (masked by: EAPI 3) That has been hitting many users with pre-eapi3 portage and is really frustrating. Please restore or create any version with an earlier eapi - maybe a "dummy" 1.2_pre0 would do? Thanks!
Disable USE=bash-completion during your upgrade. It's a leaf package.