Fixed test fails against OpenSSL 1.1.1.

* https://rubyci.org/logs/rubyci.s3.amazonaws.com/ubuntu/ruby-trunk/log/20181203T093003Z.fail.html.gz
  * https://rubyci.org/logs/rubyci.s3.amazonaws.com/arch/ruby-trunk/log/20181203T090002Z.fail.html.gz

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@66163 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

lib/rubygems/remote_fetcher.rb

@@ -274,7 +274,7 @@ class Gem::RemoteFetcher
     raise
   rescue Timeout::Error
     raise UnknownHostError.new('timed out', uri.to_s)
-  rescue IOError, SocketError, SystemCallError => e
+  rescue IOError, SocketError, SystemCallError, OpenSSL::SSL::SSLError => e
     if e.message =~ /getaddrinfo/
       raise UnknownHostError.new('no such name', uri.to_s)
     else