It looks like this is a revision whose log message isn't in UTF-8 for some reason. We'll have to add some kind of handling to cope with this situation.
Let's assume this was fixed by:
user: David Schleimer <email@example.com>
date: Thu May 17 14:15:14 2012 -0700
files: hgsubversion/replay.py tests/fixtures/invalid_utf8.sh tests/fixtures/invalid_utf8.tar.gz tests/test_fetch_command.py tests/test_util.py
Ignore invalid utf8 in commit messages
Old svn allowed users to include invalid utf8 in their commits. Since
there are real repos with said invalid utf8, we need to be able to
import them, even if svn won't.