Retitled this bug report since it seems to be specific to Python 3.
rstplugin is probably more commonly used with Python 2. It seems likely that there is some Python-3-specific bug in
proxy.py, perhaps introduced by commit 154c4ea "properly encode and decode from/to utf8 when sending rpc to ikiwiki".
I can reproduce this on Debian by installing
python3-docutilsand changing the first line of
plugins/proxy.py, the first line of
plugins/pythondemo, the first line of
looks like the problem is in proxy.py
ml = IkiWikiExtPluginXMLRPCHandler.read(in_fd).decode('utf8')
without decode('utf8') is working
tested and fixed with patch http://git.pseudorandom.co.uk/smcv/ikiwiki.git/commitdiff/38bd51bc1bab0cabd97dfe3cb598220a2c02550a and patch http://git.pseudorandom.co.uk/smcv/ikiwiki.git/commitdiff/81506fae8a6d5360f6d830b0e07190e60a7efd1c