The fix looks appropriated (and using HTTPS is always better), but the tests must be updated.

right :) i dont want to add unnecessary effort for mergers. So perhaps it's better to do it globally per branch, 3.4 and up, or keep the legacy.

sed -i -E 's/http:\/\/symfony.com\/schema\/dic\/([^\ ]+)\.xsd/https:\/\/symfony.com\/schema\/dic\/\1.xsd/g' src/**/*.{xml,php}

this should indeed be done in 3.4 and up to avoid merge conflicts in the future.

i was mainly curious if we we want to update all test fixtures and core configs as well...

if it's only for the dumped container, it also qualifies a new feature (but i should fix the tests properly, per case then)

I would update core configs as well. For testing configs I think we don't really care, would be bonus :)

(rebase needed)

see #30434