Returns a new search object with filterstr and-ed to the original filter
        string. The caller is responsible for passing in a properly escaped
        string.

def search_with_additional_term_string(self, filterstr):
        """
        Returns a new search object with filterstr and-ed to the original filter
        string. The caller is responsible for passing in a properly escaped
        string.
        """
        filterstr = u'(&%s%s)' % (self.filterstr, filterstr)

        return self.__class__(self.base_dn, self.scope, filterstr)