TypeError: unicode argument expected, got 'str'

[Ryan J Ollos]

Found in the logs,

[pid 24004 139801362245376] 2017-06-19 08:03:12,877 Trac[formatter] ERROR: Processor html failed for <Resource u'wiki:SandBox@165'>:
Traceback (most recent call last):
  File "/usr/local/virtualenv/1.3dev/lib/python2.7/site-packages/trac/wiki/formatter.py", line 1195, in _exec_processor
    return processor.process(text)
  File "/usr/local/virtualenv/1.3dev/lib/python2.7/site-packages/trac/wiki/formatter.py", line 375, in process
    text = self.processor(text)
  File "/usr/local/virtualenv/1.3dev/lib/python2.7/site-packages/trac/wiki/formatter.py", line 228, in _html_processor
    return self._sanitizer.sanitize(text)
  File "/usr/local/virtualenv/1.3dev/lib/python2.7/site-packages/trac/util/html.py", line 645, in sanitize
    transform.feed(html)
  File "/usr/lib/python2.7/HTMLParser.py", line 117, in feed
    self.goahead(0)
  File "/usr/lib/python2.7/HTMLParser.py", line 222, in goahead
    self.handle_data("&")
  File "/usr/local/virtualenv/1.3dev/lib/python2.7/site-packages/trac/util/html.py", line 1012, in handle_data
    self.out.write(data)
TypeError: unicode argument expected, got 'str'

I've been seeing the error in the logs for a week or two, but until we upgraded to the latest Trac trunk with improved logging, couldn't see that the exception was being raised from SandBox@165.