This traceback was been provided for advice on IRC tonight:
2012-10-03 13:53:12,425 Trac[main] ERROR: Internal Server Error:
Traceback (most recent call last):
File "/usr/lib/python2.7/dist-packages/trac/web/main.py", line 511, in _dispatch_request
dispatcher.dispatch(req)
File "/usr/lib/python2.7/dist-packages/trac/web/main.py", line 237, in dispatch
resp = chosen_handler.process_request(req)
File "/usr/local/lib/python2.7/dist-packages/TracWatchlistPlugin-1.0-py2.7.egg/tracwatchlist/plugin.py", line 589, in process_request
offset = req.tz.utcoffset(datetime.now(req.tz))
File "/usr/lib/python2.7/dist-packages/pytz/tzinfo.py", line 401, in utcoffset
dt = self.localize(dt, is_dst)
File "/usr/lib/python2.7/dist-packages/pytz/tzinfo.py", line 299, in localize
raise ValueError('Not naive datetime (tzinfo is already set)')
ValueError: Not naive datetime (tzinfo is already set)
Seems like recent changes to Trac break current code, as hinted by osimons.
Better use functions from trac.util.datefmt for what is needed by the plugin.