merge revision(s) 61507: [Backport #14247]
Fix KeyError#{key,receiver} of Thread#fetch [ruby-core:84508] [Bug #14247]
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/branches/ruby_2_5@61583 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
merge revision(s) 61507: [Backport #14247]
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/branches/ruby_2_5@61583 b2dd03c8-39d4-4d8f-98ff-823fe69b080e