A mirror is no primary source and should not be used as SRC_URI https://devmanual.gentoo.org/general-concepts/mirrors/
If you think mirror://gentoo is not approproate can you file a bug against repoman to complain about such SRC_URIs?
The bug has been closed via the following commit(s): https://gitweb.gentoo.org/repo/gentoo.git/commit/?id=a0395c9b00ce9c7482227c18c9fa0b5f7b172a90 commit a0395c9b00ce9c7482227c18c9fa0b5f7b172a90 Author: Fabian Groffen <grobian@gentoo.org> AuthorDate: 2019-06-08 09:17:31 +0000 Commit: Fabian Groffen <grobian@gentoo.org> CommitDate: 2019-06-08 09:17:54 +0000 app-portage/portage-utils: don't use mirror://, fix some SLOT deps Closes: https://bugs.gentoo.org/687616 Signed-off-by: Fabian Groffen <grobian@gentoo.org> Package-Manager: Portage-2.3.66, Repoman-2.3.11 .../portage-utils/portage-utils-0.80_pre20190605.ebuild | 13 ++++++------- app-portage/portage-utils/portage-utils-9999.ebuild | 13 ++++++------- 2 files changed, 12 insertions(+), 14 deletions(-)