Speed up packing time #412

Job	Run time
run / test (mysql57, pymysql)	6h 0m 10s
run / test (mysql57, mysqldb)	6h 0m 7s
run / test (mysql57, asyncmy)	6h 0m 13s
run / test (mysql57, mariadbconnector)	6h 0m 14s
run / test (mysql80, pymysql)	6h 0m 13s
run / test (mysql80, mysqldb)	6h 0m 14s
run / test (mysql80, asyncmy)	6h 0m 13s
run / test (mysql80, mariadbconnector)	6h 0m 15s
run / test (mysql84, pymysql)	6h 0m 14s
run / test (mysql84, mysqldb)	6h 0m 14s
run / test (mysql84, asyncmy)	6h 0m 15s
run / test (mysql84, mariadbconnector)	6h 0m 14s
run / test (mysql90, pymysql)	6h 0m 14s
run / test (mysql90, mysqldb)	6h 0m 13s
run / test (mysql90, asyncmy)	6h 0m 14s
run / test (mysql90, mariadbconnector)	6h 0m 13s
run / summarize	1s
	4d 0h 3m 31s

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