Please add a QA check that's going to forbid developers from using 'simple filenames' in SRC_URI if RESTRICT=fetch is not being used. I mean cases like: SRC_URI="${P}.tar.gz" where some developers assume to be implicit form of mirror://gentoo. In fact, Portage may seem to do that but it's only using user-defined GENTOO_MIRRORS, so with no mirrors defined in configuration, it's going to fail hard. And this is not something that should be done in ::gentoo.
repoman support has been removed per bug 835013. Please file a new bug (or, I suppose, reopen this one) if you feel this check is still applicable to pkgcheck and doesn't already exist.