class Gem::UnknownCommandError

def self.attach_correctable
  return if defined?(@attached)
  if defined?(DidYouMean::SPELL_CHECKERS) && defined?(DidYouMean::Correctable)
    if DidYouMean.respond_to?(:correct_error)
      DidYouMean.correct_error(Gem::UnknownCommandError, Gem::UnknownCommandSpellChecker)
    else
      DidYouMean::SPELL_CHECKERS["Gem::UnknownCommandError"] =
        Gem::UnknownCommandSpellChecker
      prepend DidYouMean::Correctable
    end
  end
  @attached = true
end

def initialize(unknown_command)
  self.class.attach_correctable
  @unknown_command = unknown_command
  super("Unknown command #{unknown_command}")
end