Bug#952088: sync is not longer bundled, but a gem

[Daniel Leidert]

The test in Ruby 2.7 fails because the sync library has been split out in Ruby
2.6 and is now available as a gem:
https://www.ruby-lang.org/en/news/2019/12/25/ruby-2-7-0-released/

signature.asc
Description: This is a digitally signed message part