def process_exception(exception) #:nodoc:
      if @error_callback
        @error_callback.call(message, exception)
      else
        error(exception)
      end
    rescue Exception
      Beetle::reraise_expectation_errors!
    end
def process_exception(exception) #:nodoc:
      if @error_callback
        @error_callback.call(message, exception)
      else
        error(exception)
      end
    rescue Exception
      Beetle::reraise_expectation_errors!
    end
should not be overriden in subclasses