[test] make unittest_webconfig independant of CWD
if apphome is unset in ApptestConfiguration constructor, this later looks
for a 'data' directory in CWD, making this test runnable only from
web/test (and pytest do chdir before executing tests, so we did not noticed
this problem).
from yams.buildobjs import RelationDefinition
class ARelation(RelationDefinition):
subject = 'CWUser'
object = 'CWGroup'