class RSpec::Expectations::LegacyMatcherAdapter::RSpec2

@private
* ‘failure_message_for_should_not`
* `failure_message_for_should`
the failure message protocol was:
Starting in RSpec 1.2 (and continuing through all 2.x releases),

def self.interface_matches?(matcher) 

def self.interface_matches?(matcher)
  (
    !matcher.respond_to?(:failure_message) &&
    matcher.respond_to?(:failure_message_for_should)
  ) || (
    !matcher.respond_to?(:failure_message_when_negated) &&
    matcher.respond_to?(:failure_message_for_should_not)
  )
end

def failure_message 

def failure_message
  base_matcher.failure_message_for_should
end

def failure_message_when_negated 

def failure_message_when_negated
  base_matcher.failure_message_for_should_not
end