py3: use pycompat.bytestr so that we don't get ascii values
This fixes `hg files 'set:(**.py)'` which makes test-check-py3-compat.t able to
run on Python 3. So if you now do `python3 ./run-tests.py
test-check-py3-compat`, the test will actually run.
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273ce12ad8f1` will report some style violations on a very old commit).