'Check if any rows are returned from the submitted where statement.
If there are, then this will throw an AssertionError.
Usage:
Row count is zero  (s3db.pr_contact.value == "af_editor@example.com")
... & (s3db.pr_contact.contact_method == "EMAIL")
False'

def row_count_is_zero(self, statement):

    count = self.row_count(statement)
    if (count != 0):
        raise AssertionError(('Expected    the    count    to    be    zero    from    %s    but                                                    it    was    %d    instead' % (statement, count)))
