py3: don't index into bytes in phabricator's _tokenize()
`phabread`ing a stack using `hg phabread :D1234` under py3 will currently die
with a KeyError because it will index into `b':D1234'` and return `58` instead
of `b':'` as a token.
Differential Revision: https://phab.mercurial-scm.org/D7129
$ hg init
$ echo 123 > a
$ hg add a
$ hg commit -m "first" a
$ mkdir sub
$ echo 321 > sub/b
$ hg add sub/b
$ hg commit -m "second" sub/b
$ cat sub/b
321
$ hg co 0
0 files updated, 0 files merged, 1 files removed, 0 files unresolved
$ cat sub/b 2>/dev/null || echo "sub/b not present"
sub/b not present
$ test -d sub || echo "sub not present"
sub not present