set journal mode to wal when creating db. Trying to work around sqlite3.OperationalError: disk I/O error errors in CI that I can't reproduce locally. Also this allows reads to happen while writes are occurring. This should permit using the web interface for browsing while a large write load (e.g. bulk data loading from another tracker) is happening. Right now autogenerating issues locks up the tracker for reading with an error that the database is locked.

def init_severity(db, cl, nodeid, newvalues):
    """Make sure severity is set on new issues"""
    if 'severity' in newvalues and newvalues['severity']:
        return

    normal = db.severity.lookup('normal')
    newvalues['severity'] = normal

def init(db):
    db.issue.audit('create', init_severity)