In bug 721752, we're tracking ebuilds requiring Python which do not have Python >= 3.7 in their stable version, but support >= 3.7 in a newer unstable version. This is problematic when the make.defaults change to e.g. PYTHON_TARGETS="python3_7" and e.g. layman (bug 720934) stops the upgrade with a cryptic error. I see this as equivalent to a stable ebuild depending on something unstable, but maybe others' views will differ. In any case, this situation causes confusion for users and some QA flag to notify when make.defaults conflicts with ebuilds would be useful. I propose: flag when PYTHON_TARGETS (and similar variables?) in make.defaults "breaks" ability to install ebuilds because of their (lack of) stable keywords.
*** This bug has been marked as a duplicate of bug 540334 ***
(In reply to Sam James from comment #1) > > *** This bug has been marked as a duplicate of bug 540334 *** nevermind!
We have RequiredUseDefaults in pkgcheck.