ruby stack trace:

/usr/local/lib/ruby/2.1.0/net/ftp.rb:327:in `getresp'
/usr/local/lib/ruby/2.1.0/net/ftp.rb:339:in `voidresp'
/usr/local/lib/ruby/2.1.0/net/ftp.rb:584:in `block (2 levels) in storlines'
/usr/local/lib/ruby/2.1.0/net/ftp.rb:199:in `with_binary'
/usr/local/lib/ruby/2.1.0/net/ftp.rb:572:in `block in storlines'
/usr/local/lib/ruby/2.1.0/monitor.rb:211:in `mon_synchronize'
/usr/local/lib/ruby/2.1.0/net/ftp.rb:571:in `storlines'