Your bundle is locked to extlib (0.9.16), but that version could not be found in any of the sources listed in your Gemfile

migration-paths jobs on master are failing with this error:

Your bundle is locked to extlib (0.9.16), but that version could not be found in
any of the sources listed in your Gemfile. If you haven't changed sources, that
means the author of extlib (0.9.16) has removed it. You'll need to update your
bundle to a version other than extlib (0.9.16) that hasn't been removed in order
to install.

https://gitlab.com/gitlab-org/gitlab-ce/-/jobs/140317256

I haven't seen any other jobs fail with exactly this message, but we have seen QA failures with a similar message: https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/24091

One thing I don't quite understand is why the migration-paths jobs do this:

    - sed -i "s/gem 'oj', '~> 2.17.4'//" Gemfile
    - bundle update google-protobuf grpc

As it's when we run bundle update that we get the failure.