'Raise exception for extra {% extends %} tags'

@setup({'exception03': "{%    extends    'inheritance01'    %}{%    block    first    %}2{%    endblock    %}{%    extends    'inheritance16'    %}"}, inheritance_templates)
def test_exception03(self):

    with self.assertRaises(TemplateSyntaxError):
        self.engine.get_template('exception03')
