use pjoin from snakeoil and sort imports
restructure fakerepo setup for formatting tests
conditionalize the output for the pkg version being replaced

Previously it would only be shown for pkgs being upgraded or downgraded.
This misses the case where a pkg switches between repos. Note that it
will only show the unchanged version not including the changed repo_id
if verbose output is disabled, but this signifies an underlying change
(more than just a straight pkg rebuild) and matches current portage
output.