# File lib/rspec/expectations/handler.rb, line 5
      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