def start(self, context):
if __debug__:<EOL><INDENT>log.info("<STR_LIT>", extra=dict(<EOL>uri = redact_uri(self.uri),<EOL>config = self.config,<EOL>alias = self.alias,<EOL>))<EOL><DEDENT>engine = self.engine = create_engine(self.uri, **self.config)<EOL>self.Session = scoped_session(sessionmaker(bind=engine))<EOL>engine.connect().close()<EOL>context.db[self.alias] = engine<EOL>
Construct the SQLAlchemy engine and session factory.