class RSpec::Expectations::ExpectationHandler

def self.check_message(msg)
  unless msg.nil? || msg.respond_to?(:to_str) || msg.respond_to?(:call)
    ::Kernel.warn [
      "WARNING: ignoring the provided expectation message argument (",
      msg.inspect,
      ") since it is not a string or a proc."
    ].join
  end
end