def setup(self):
        """
        Performs some checks.

        :return: None if successful, otherwise error message.
        :rtype: str
        """
        result = super(BranchDirector, self).setup()
        if result is None:
            try:
                self.check_actors()
            except Exception, e:
                result = str(e)
        return result
Performs some checks.

        :return: None if successful, otherwise error message.
        :rtype: str