> Hmm.  Given the presence of 'mac_roman.py' in the traceback, I wonder if
> Issue 6202 has any relevance here?

Only partially so. That character (LATIN SMALL LETTER C WITH ACUTE) is
not supported by Mac-roman, so the codec is right in complaining that it
can't encode it. And yes, had svnmerge been run in an UTF-8 locale, it
would have worked fine.

However, I think it is svnmerge that is to blame here. It implements
construct_merged_log_message, which really should do its job in a
locale-independent way - as long as it uses the locale encoding, it
can always run into problems.

Fortunately, svn has been support --xml for "svn log" for a number of
releases. So svnmerge should switch to use that; it will allow parsing
arbitrary characters in a log message, independent of what the terminal
encoding is.