instance method generate_local_secret

# File railties/lib/rails/application/configuration.rb, line 693
        def generate_local_secret
          key_file = root.join("tmp/local_secret.txt")

          random_key = begin
            File.binread(key_file)
          rescue SystemCallError
            nil
          end

          return random_key if random_key.present?

          random_key = SecureRandom.hex(64)
          FileUtils.mkdir_p(key_file.dirname)
          File.binwrite(key_file, random_key)
          random_key
        end