UnicodeDecodeError on mail processing

[Cyril B.]

This is on the latest trunk (7232), with Python 2.7.5, when sending a message with an accent (e.g. 'é'):

Jan 20 18:19:04 2014 (1377272) ACCEPT: <email address hidden>
Jan 20 18:19:05 2014 (1377274) Uncaught runner exception: 'ascii' codec can't decode byte 0xe9 in position 5: ordinal not in range(128)
Jan 20 18:19:05 2014 (1377274) Traceback (most recent call last):
  File "/home/cbay/mailman/python/lib/python2.7/site-packages/mailman/core/runner.py", line 169, in _one_iteration
    self._process_one_file(msg, msgdata)
  File "/home/cbay/mailman/python/lib/python2.7/site-packages/mailman/core/runner.py", line 252, in _process_one_file
    keepqueued = self._dispose(mlist, msg, msgdata)
  File "/home/cbay/mailman/python/lib/python2.7/site-packages/mailman/runners/pipeline.py", line 36, in _dispose
    process(mlist, msg, msgdata, pipeline)
  File "/home/cbay/mailman/python/lib/python2.7/site-packages/mailman/core/pipelines.py", line 66, in process
    handler.process(mlist, msg, msgdata)
  File "/home/cbay/mailman/python/lib/python2.7/site-packages/mailman/handlers/to_digest.py", line 58, in process
    mbox.add(msg)
  File "/home/cbay/mailman/python/lib/python2.7/mailbox.py", line 587, in add
    self._toc[self._next_key] = self._append_message(message)
  File "/home/cbay/mailman/python/lib/python2.7/mailbox.py", line 743, in _append_message
    offsets = self._install_message(message)
  File "/home/cbay/mailman/python/lib/python2.7/mailbox.py", line 805, in _install_message
    self._dump_message(message, self._file, self._mangle_from_)
  File "/home/cbay/mailman/python/lib/python2.7/mailbox.py", line 212, in _dump_message
    buffer.seek(0)
  File "/home/cbay/mailman/python/lib/python2.7/StringIO.py", line 106, in seek
    self.buf += ''.join(self.buflist)
UnicodeDecodeError: 'ascii' codec can't decode byte 0xe9 in position 5: ordinal not in range(128)
Jan 20 18:19:05 2014 (1377274) SHUNTING: 1390238345.418067+c3cd5177d093930a97531fcfccd6d1e08ae57b4e