'Return a rels_elm mock that will be returned from
CT_Relationships.new()'

@pytest.fixture
def rels_elm(self, request):

    rels_elm = Mock(name=u'rels_elm')
    xml = PropertyMock(name=u'xml')
    type(rels_elm).xml = xml
    rels_elm.attach_mock(xml, u'xml')
    rels_elm.reset_mock()
    patch_ = patch.object(CT_Relationships, u'new', return_value=rels_elm)
    patch_.start()
    request.addfinalizer(patch_.stop)
    return rels_elm
