Safety level may not be changed inside a transaction on SQLite with synchronous=normal if PySqlite 2.8.1 (3.8.2)

[Jun Omae]

2016-03-28 00:56:58,865 Trac[pool] ERROR: Exception caught on create
Traceback (most recent call last):
  File "/home/jun66j5/src/tracdev/svn/branches/1.0-stable/trac/db/pool.py", line 105, in get_cnx
    cnx = connector.get_connection(**kwargs)
  File "/home/jun66j5/src/tracdev/svn/branches/1.0-stable/trac/db/sqlite_backend.py", line 190, in get_connection
    return SQLiteConnection(path, log, params)
  File "/home/jun66j5/src/tracdev/svn/branches/1.0-stable/trac/db/sqlite_backend.py", line 298, in __init__
    _set_synchronous(cursor, params.get('synchronous'))
  File "/home/jun66j5/src/tracdev/svn/branches/1.0-stable/trac/db/sqlite_backend.py", line 408, in _set_synchronous
    cursor.execute('PRAGMA synchronous = %s' % _quote(value))
OperationalError: Safety level may not be changed inside a transaction
2016-03-28 00:56:58,865 Trac[chrome] ERROR: Error during check of EMAIL_VIEW: TimeoutError: Unable to get database connection within 0 seconds. (OperationalError: Safety level may not be changed inside a transaction)