[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 os.path import join
assert __file__.endswith(join('scripts', 'script1.py')), __file__
assert '__main__' == __name__, __name__
assert [] == __args__, __args__