Since commit 1032cbf4c218741df1c57767fead2d00cc6321d9, tests fail because _LazyImportFrom._get_target does not try to import submodules.
There's a patch in the following branch: https://github.com/zmedico/portage/tree/bug_550906 I've posted it for review here: https://archives.gentoo.org/gentoo-portage-dev/message/83e389945fb556f007dd0331c03f0a49
This is in the master branch: https://gitweb.gentoo.org/proj/portage.git/commit/?id=7a63f955b8da06c565ea342975014511b1cc2bd3
Released in portage-2.2.21