obsolete: use bytes() instead of str() so the node is bytes on py3
I'm not sure this is right, since this should either be bytes or str
to match what's going on in the revlog layer.
Differential Revision: https://phab.mercurial-scm.org/D271
tests: fix test-notify.t to use $PYTHON
In doing so, I consolidated the filtering logic. This resulted in some
small test output changes, but I think the consistency throughout the
test is worth it.
Differential Revision: https://phab.mercurial-scm.org/D279