経緯 Rubyを2.3系から2.4.1に上げたら、ActiveSupport::MessageEncryptorを使っているところが壊れた。ちなみにRailsは5.0.1。 key must be 32 bytes /Users/nisshiee/.rbenv/versions/2.4.1/lib/ruby/gems/2.4.0/gems/activesupport-5.0.1/lib/active_support/message_encryptor.rb:79:in `key=' /Users/nisshiee/.rbenv/versions/2.4.1/lib/ruby/gems/2.4.0/gems/activesupport-5.0.1/lib/active_support/message_encryptor.rb:79:in `_encrypt' /Users/nisshiee/