run-tests: fix escapes with conditions Before this fix, escapes with conditions in tests failed like this on Python 3: $ $PYTHON -c 'from mercurial.utils.procutil import stdout; stdout.write(b"\xff")' - \xff (no-eol) (esc) (true !) + \xff (no-eol) (esc) The unicode_escape encoding decodes br'\xff' to u'\xff'. To convert the first 256 code points to bytes with the same ordinal, the latin-1 encoding must be used. Escapes without conditions already worked before on Python 3, but not through `el == l` a few lines below the changed line in run-tests.py. I didn’t investigate further.