Initialise the "logs" table in the db.

def _init_logs_table():
    """Initialise the "logs" table in the db."""
    _logs_table = sqlalchemy.Table(
        'logs', _METADATA,
        sqlalchemy.Column(
            'job_id', sqlalchemy.ForeignKey("jobs.job_id", ondelete="CASCADE"),
            nullable=False),
        sqlalchemy.Column('timestamp', sqlalchemy.DateTime),
        sqlalchemy.Column('message', sqlalchemy.UnicodeText),
        sqlalchemy.Column('level', sqlalchemy.UnicodeText),
        sqlalchemy.Column('module', sqlalchemy.UnicodeText),
        sqlalchemy.Column('funcName', sqlalchemy.UnicodeText),
        sqlalchemy.Column('lineno', sqlalchemy.Integer)
        )
    return _logs_table