tests: use `f --hexdump` to print file content The inline print.py in this test wasn't fully compatible with Python 3 because it was reading from sys.stdin, which already normalized line endings since it operates in the realm of str on Python 3. To do this correctly, we'd need to read from sys.stdin.buffer on Python 3. This would entail conditional code. I felt this was too much effort. So I just replaced the custom script with `f`, which already knows how to do the right thing. test-mactext.t now passes on Python 3 on Windows. Differential Revision: https://phab.mercurial-scm.org/D8336