After having a second look at this deprecation, the explanation that
we're giving does not make a lot of sense. When working only with local
gems, Bundler will indeed generate a different lockfile depending on
the latest installed version of each gem is at `bundle install` time.

That's the same situation that happens with remote sources: Bundler will
generate a different lockfile depending on the latest version of each
gem available remotely.

So, I don't think "a consistent lockfile not getting generated" is a
good motivation for deprecating this.

Also, this deprecation brings additional challenges, since for example,
it should arguably not get printed when using `bundle install --local`?

The original problem when this deprecation was introduced was an
incorrect message about a missing gem having been yanked.

So, I think a better solution is to, as long as we give proper error
messages when things go wrong, let users do what's best for them and
undo the deprecation.

https://github.com/rubygems/rubygems/commit/17499cb83f