[ruby/psych] Fixing compatibility with libyaml 0.2.5
The main issue is that commas aren't allowed in local tags. libyaml
was updated to follow the spec, and our tests were out of date.
See: https://github.com/yaml/libyaml/issues/1963f5e520fd3
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/branches/ruby_2_6@67884 b2dd03c8-39d4-4d8f-98ff-823fe69b080e