cleanup: hgdemandimport.tracing accepts strings, not bytes
This does mean that the resulting traces will have some b'' goo in them on
Python 3, but I think that's a worthwile price to pay since it doesn't break
any tests.
Differential Revision: https://phab.mercurial-scm.org/D7108
https://bz.mercurial-scm.org/1089
$ hg init
$ mkdir a
$ echo a > a/b
$ hg ci -Am m
adding a/b
$ hg rm a
removing a/b
$ hg ci -m m a
$ mkdir a b
$ echo a > a/b
$ hg ci -Am m
adding a/b
$ hg rm a
removing a/b
$ cd b
Relative delete:
$ hg ci -m m ../a
$ cd ..