If you are using ocaml-ci-scripts to run your CI scripts using Travis CI, Circle CI or Appveyor, you should know that since a few minutes ago, the default images and scripts are using opam2-rc4.
Normally, the change should be completely transparent: everything should continue to work as before. If that’s not the case, you could revert to use opam 1.2.2 by setting
OPAM_VERSION=1.2.2 in your
.travis.yml script and please report the issue so that we can fix it before the release planned in September.