Looks like this has been modified by hand and is missing a line:
```
➜  govuk_offsitebackups-puppet git:(vagrant-adddiscs) b librarian-puppet install
/Users/dcarley/vendor/bundle/gems/librarian-puppet-0.9.13/lib/librarian/puppet/lockfile/parser.rb:41:in `parse': Expected DEPENDENCIES topic! (StandardError)
…
```