portage is blocked by “the current version of portage supports EAPI ‘6’. You must upgrade”

We’ve synced the portage tree before upgrading our old portage package (big mistake! always upgrade the portage package before sync) and then do the sync. After the sync the portage upgrade was impossible, because a dependency package supported only a new portage API (probably a new package) in our case EAPI 7 and the offensive package was “app-eselect/eselect-pinentry“.
So there are two options:

  1. Find the last version of the portage,which does not depend on the package – app-eselect/eselect-pinentry
  2. Find if some of the USE flags disable the inclusion of this dependency – app-eselect/eselect-pinentry

We chose the second option and found that if we compiled the portage package with

-rsync-verify

the portage did not pull the dependency “app-eselect/eselect-pinentry” and then after a successful upgrade we had the portage supported EAPI 7 and reinstalled it with activated “-rsync-verify”.
Keep on reading!