I would like to stabilize RubyCI.

https://rubyci.org/logs/rubyci.s3.amazonaws.com/fedora26/ruby-trunk/log/20180205T123003Z.fail.html.gz

downloading did_you_mean-1.2.0.gem ... /home/hsbt/chkbuild/tmp/build/20180205T123003Z/tmp/ruby-snapshot20180205-23226-3201ha/ruby-2.6.0-r62226/tool/downloader.rb:212:in `rescue in download': failed to download did_you_mean-1.2.0.gem (RuntimeError)
SocketError: Failed to open TCP connection to rubygems.org:443 (getaddrinfo: Name or service not known): https://rubygems.org/downloads/did_you_mean-1.2.0.gem
	from /home/hsbt/chkbuild/tmp/build/20180205T123003Z/tmp/ruby-snapshot20180205-23226-3201ha/ruby-2.6.0-r62226/tool/downloader.rb:123:in `download'
	from /home/hsbt/chkbuild/tmp/build/20180205T123003Z/tmp/ruby-snapshot20180205-23226-3201ha/ruby-2.6.0-r62226/tool/downloader.rb:66:in `download'
	from -e:4:in `<main>'
make[1]: *** [Makefile:1685: update-gems] Error 1

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@62231 b2dd03c8-39d4-4d8f-98ff-823fe69b080e