OperationalError: (1241, 'Operand should contain 1 column(s)')

[Ryan J Ollos]

2018-06-01 01:32:49,607 Trac[main] ERROR: [206.47.39.180] Internal Server Error: <RequestWithSession "GET '/milestone/1.10?by=owner&by=owner'">, referrer 'https://bugs.jquery.com/milestone/1.10?by=owner'
Traceback (most recent call last):
  File "/var/www/bugs.jquery.com/private/pve/local/lib/python2.7/site-packages/trac/web/main.py", line 623, in _dispatch_request
    dispatcher.dispatch(req)
  File "/var/www/bugs.jquery.com/private/pve/local/lib/python2.7/site-packages/trac/web/main.py", line 239, in dispatch
    resp = chosen_handler.process_request(req)
  File "/var/www/bugs.jquery.com/private/pve/local/lib/python2.7/site-packages/trac/ticket/roadmap.py", line 766, in process_request
    return self._render_view(req, milestone)
  File "/var/www/bugs.jquery.com/private/pve/local/lib/python2.7/site-packages/trac/ticket/roadmap.py", line 1000, in _render_view
    field=by)
  File "/var/www/bugs.jquery.com/private/pve/local/lib/python2.7/site-packages/trac/ticket/roadmap.py", line 312, in get_tickets_for_milestone
    for tkt_id, status, fieldval in env.db_query(sql, args)]
  File "/var/www/bugs.jquery.com/private/pve/local/lib/python2.7/site-packages/trac/db/api.py", line 122, in execute
    return db.execute(query, params)
  File "/var/www/bugs.jquery.com/private/pve/local/lib/python2.7/site-packages/trac/db/util.py", line 128, in execute
    cursor.execute(query, params if params is not None else [])
  File "/var/www/bugs.jquery.com/private/pve/local/lib/python2.7/site-packages/trac/db/util.py", line 72, in execute
    return self.cursor.execute(sql_escape_percent(sql), args)
  File "/var/www/bugs.jquery.com/private/pve/local/lib/python2.7/site-packages/MySQLdb/cursors.py", line 205, in execute
    self.errorhandler(self, exc, value)
  File "/var/www/bugs.jquery.com/private/pve/local/lib/python2.7/site-packages/MySQLdb/connections.py", line 36, in defaulterrorhandler
    raise errorclass, errorvalue
OperationalError: (1241, 'Operand should contain 1 column(s)')