Triggered by another bug, it is found that package py has content that does not support python3. /usr/lib64/python3.2/site-packages/py/_io/terminalwriter.py def _getbytestring(self, s): # XXX review this and the whole logic if self.encoding and sys.version_info[0] < 3 and isinstance(s, unicode): etc The module unicode no longer exists. The function fails under at least python3.
That's why it checks sys.version_info[0]. Works for me.